Thus, the bell now tolls for Facebook Founder Mark Zuckerberg.

We at BoomTown have been consistent and persistent in voicing our various worries about the young entrepreneur, from one of our very first posts, questioning (we think fairly) the unproven business underpinnings of the hot social network, the juvenile nature of its much vaunted third-party widgets, the insanity of its $15 billion valuation, its inane legal fights and the problems with its worrisome ad efforts.

We’ve also taken (we think probably unfairly) shots at those flip-flops he wears. And we did call him a toddler CEO, also a low blow, we have to admit.

But now, it seems, a mob is forming, sparked by the issues around Facebook’s controversial Beacon ad program, which can track your purchases on some external sites and send the information back to your Facebook profile’s news feed.

While it made some changes in Beacon last week, Facebook has not given users a global opt-out of the controversial marketing system in which the social network is seeking to link behavior and advertising more tightly for supposedly bigger payoffs.

The mainstream media and blogosphere, which recently were feting him, have now turned and ire has been growing over Beacon, which seems to be focusing everyone on the inexperience of Zuckerberg and the challenges facing Facebook.

That was clear in a very cogent piece by Josh Quittner on his Techland blog for Fortune today, which was titled “RIP Facebook?”

He writes:

A lot of people say that Facebook has jumped the shark. That’s flat out wrong. In fact, Facebook is now being devoured by the shark. There’s so much blood in the water, it’s attracting other sharks. And if Facebook’s not careful, one of them is bound to come along and finish it off. I’ve never seen anything like it in the annals of fast-rising tech companies that fail.”

As Zuckerberg might say: That bites.

And here is a photo that was put on the Fake Steve Jobs blog, which was using the PhotoCrank service, where users can add captions:

Oh my.

As Quittner writes correctly, right now it is the press that has turned on Zuckerberg, which is sure to be followed by much more important advertisers, who shy away from controversy.

We’ll see how it plays out, but it is surely a flash point moment for Facebook.

Or in the immortal words of actress Joan Crawford: “Love is a fire. But whether it is going to warm your hearth or burn down your house, you can never tell.”

Feel the love, Mark.

Poor Facebook VP Owen Van Natta–locked away all day on such a lovely Bay area weekend.

He and other Facebook execs spent Saturday and Sunday blabbing away with potential partners into the night, as Facebook looks to complete a commercial deal with either Yahoo, Google or Microsoft to serve its international ads.

But the execs are also trying to nail down a big funding that will potentially give the hotsy-totsy social network a giant slug of cash, as well as a lofty $15 billion valuation.

No deal as yet, but sources close to Facebook said it was now a horse race between Microsoft, which already serves Facebook’s ads in the U.S., and Google. Yahoo, sources said, is a long-shot dark horse in the bidding.

According to sources, Google is not as keen to make a big investment in Facebook (although it would be willing to make a token one), preferring that most of the funding come from private equity investors. It is also driving a harder bargain related to guaranteed ad revenues.

Microsoft, sources have said, is more interested in a bigger investment, although the company is not as willing to completely redo its current ad deal with Facebook or make an international one that would disadvantage it considerably more.

BoomTown has pretty much been out in front of most of the Facebook coverage of late, questioning the start-up’s still nascent business plan (or lack thereof) and purplish press hype, the ridiculousness of the explosive valuation and, most recently, the juvenile nature of its vaunted third-party apps offering.

I have been a bit tough on Facebook, but for good reason. As much as I think the social network is powerful in its potential, is a terrific product that knits together a truly unique user experience and represents a leap forward in how consumers use the Web on a daily basis, I also believe its underpinnings must be examined more closely.

In other words, the massive hype around Facebook needs some serious de-hyping.

Still, as Valleywag correctly reported here, I have what is a pretty big conflict of interest (Google exec Megan Smith, whom I affectionately like to call “The Useless One”) related to the particular current deal being discussed with Google, I am going to bow out of analyzing this specific deal closely, except to point to my past writings on Facebook, including breaking news of Google’s interest in Facebook.

(Please take time again to read my long disclosure on the issues related to Google and me.)

That does not mean I do not hope to break news of what Facebook finally manages to decide to do, both with regard to partners and its funding, but that I will bow out of parsing this deal in excessive detail.

(In sum, though, my coverage so far: An overhyped IPO might provide cover, but good luck making serious money on Facebook ads, whichever one of you solar-powered brainiacs, you software behemoths, you sacred cow disrespecters wins! At this point, I remain solidly dubious.)

That Hollywood term refers to giving Pepsi Entertainment the first opportunity to be part of any idea the pair develops. Pepsi could then pass on whatever concept it wants to, even though it might still have a financial interest in the content.

Berman, Braun and Pepsi executives would not be specific about the financing agreements between them or other details about the type of content they will be creating, although such material is likely to cost well under a million dollars per project, relatively inexpensive by old-media standards.

But both sides touted the arrangement as a new kind of marketing and entertainment partnership designed to take advantage of trends toward increased interactivity by consumers, especially younger ones.

“We want to create great online content … and also something that is more than a glorified Internet ad at the same time,” said Braun today. “So we’ll work with Pepsi hand-in-hand to bake new kinds of ad solutions right in organically at the earliest possible moment.”

Pepsi officials said the more interactive nature of sites like Facebook and MySpace meant it needed to look for all sorts of different ways to touch consumers, well beyond techniques in place now that still center on click-through banner ads.

“A lot of online content is already developed and ads and marketing are slapped on afterward,” said Russell Weiner, vice president of marketing for colas at Pepsi-Cola North America, whose brands include the flagship Pepsi, as well as Mountain Dew, Aquafina and Sierra Mist. “We want to be part of the DNA of a show from the very beginning.”

What that means is unclear, and both sides said that just creating too-obvious Pepsi tie-ins would not work.

While a lot of other independent producers like Mark Burnett work closely with advertisers from the start, which essentially results in a lot of product placement, Berman and Braun hope to change the way marketing messages are integrated into content and, perhaps more important, how content online will be funded.

So far, that part of the equation has been a vexing one, with no clear “hits” on the Web as yet, except for viral user-generated content on sites like YouTube.

Although many sites pull in big traffic, like the AOL-owned celebrity site TMZ.com, most professionally produced content has had less success. There have been a lot of single successes, like the popular JibJab cartoon satires.

Braun said he had hoped to change that at Yahoo, which once had big plans to enter this arena, capped by Braun’s hiring by former CEO Terry Semel. It did not work out that way for a variety of reasons, including a pullback by Yahoo and shift of resources to search products.

But he did have a good experience with Pepsi with the creation of one popular property on Yahoo, “The 9,” a daily online show about hot entertainment and digital trends. Pepsi is still the site’s sponsor; the 10th link of the day is called the Pepsi 10 and is selected by a user.

Braun said he went right to the beverage company after he left Yahoo and he and Berman formed their Los Angeles-based production company BermanBraun.

While they have both called it a “multiplatform” company and said they wanted to include Internet and film elements, its first deal was with NBC Universal, giving it a first look at content they produce for television.

Berman has long been considered one of the most powerful women in Hollywood, but left her job as president of Paramount in January after a corporate shake-up.

And Braun’s rocky tenure as head of Yahoo’s Media Group ended in February, with Braun leaving the Internet giant without completing the ambitious online entertainment plans he was brought in to shepherd.

Both Berman and Braun, close personal friends, were also longtime competitors–she ran the entertainment arm of the Fox network for five years starting in 2000, while Braun headed ABC’s entertainment efforts until he went to Yahoo in 2004.

Both are longtime hit-makers: Berman is credited with green-lighting shows like “Buffy the Vampire Slayer” and “24,” while Braun is credited with pushing “Lost” onto the air.

After all this big-company experience, both were looking for a new setup, based on the indie-model with a twist.

“We have always seen this as a cross-platform company,” said Berman. “It is sort of a mini-studio, thinking about all the different mediums to create in.”

Berman and Braun said a head of its Internet group will soon be appointed and a digital content studio will be established in Santa Monica, Calif.

Pepsi’s Weiner said he thought Internet content creation and new ad solutions were still in their formative stages, even though his company thinks the Web will increasingly become a way for products to be marketed, well beyond simple ad placement.

He noted he had a good experience with Facebook, for example, when Pepsi did a campaign to let users design can logos, but he cannot yet imagine how it might all develop.

“I don’t even know if there will be ads attached to this content, especially if our brand is integrated well into the show,” he said. “It is so early, no one has really taken a peel off the onion yet.”

An interesting metaphor, given that Braun’s first experience with Yahoo might have been said to produce tears.

He would not comment on his tenure at Yahoo and its inability to leverage its power more effectively in the entertainment space. But he also said that he thinks it is still early in the game for the medium.

“We want to be Internet-centric, but it also has to be good from a pure entertainment perspective, while offering up something fresh to both consumers and advertisers,” he said. “This is not yesterday’s Internet.”

Are you listening, Yahoo?

Thus, I finally got a sit-down with the Money Guy at Facebook, Media Sales Vice President Mike Murphy.

I had known the affable Murphy (pictured here) only a little bit from his many years at Yahoo, which he left for Facebook in March 2006 in what now looks like a particularly prescient move, given the Internet giant’s recent ad troubles and Facebook’s seemingly high-flying trajectory.

I use the word seemingly, because no one really knows what the record or the prospects of Facebook are exactly when it comes to becoming an ad powerhouse, like Google and, yes, Yahoo, which did more than $1 billion in revenue for the current quarter, as weak as results were.

Here’s a video I made of my visit to Facebook HQ in Palo Alto, Calif., seeking answers to this and other questions from Murphy, as well as a drop-in from COO Owen Van Natta (who mimicked founder Mark Zuckerberg and called me “nasty” on this video, even as he chatted away, which questions his credibility related to my true level of meanness), PR head Brandee Barker and others.

To get a lay of the land, Facebook’s total revenues have been reported to hover around $100 million and it is profitable, execs and investors have told me many times.

I am not sure how much profit that means–and Facebook isn’t saying–due to the growth in staff and bandwidth demands of late.

Murphy, who would not confirm any total figure, told me about half their revenue was due to Facebook’s own ad efforts and the other half to a sweetheart deal the start-up struck with Microsoft to sell its banner ads with a guaranteed revenue payment that has been extended to 2011.

The Microsoft connection–made right after Google forked over $900 million in guarantees to News Corp.’s MySpace, the by-far dominant social network–is a nice padding for the company to have, of course.

But most of Facebook’s future depends on how Murphy and his team can translate its growing popularity and frequency by users into ad sales.

As some who read this blog might know, I often give hats off to founder Zuckerberg and his team for Facebook’s clean, handsome and highly usable service, as well as its growth.

But without other revenue streams like subscription fees, it needs to get its ad business really cooking and fast.

Or perhaps not so fast, according to Murphy and other execs at Facebook, who say building the core service and rolling out better features is the goal for now.

That will give them time to figure out the real options for ad growth on Facebook, including dreaming up a whole new way of marketing, which Murphy calls “return on involvement.”

I like his chutzpah using this term, and I vaguely understand it to mean the ability of a marketer to develop a closer relationship with a customer.

It’s been called at various times “conversational marketing” too, but it is the most credible idea for highly interactive Web sites like Facebook to pitch a new story to advertisers.

In fact, story is one of the ways Facebook is selling ads, allowing marketers to insert them in a targeted way into its powerful newsfeeds of its users, linking back to a marketing site on Facebook. When that happens, it can then go out to that person’s friends and so on and so on and so on.

If the marketer makes a good enough offer or is clever enough, then the impact could indeed be more significant than simply slapping up a banner and hoping for the best. Of course, there are those banners and links, too.

“Banners are great for branding, but this is a more relevant message that leverages social media,” argued Murphy, who said the ad sell is that it produces a cornucopia of “trusted referrals,” which is basically a nice phrase for leads.

How well that works is a big question, and some reports–though few have real proof–indicate that marketers are still on the fence about the effectiveness of this kind of marketing on Facebook.

Murphy bristled at this characterization, noting that it was his job to show marketers that becoming part of the conversation could be as important as much-measured click-through rates.

“It is an exceptionally different experience,” he said. “If we can help you make your idea or product relevant to a consumer and get the best involvement rate … it’s a different game.”

In any case, Murphy thinks the real point for Facebook right now is to build its user experience, which is more important than inundating the service with ads.

“We’re building a consumer experience here … and we’re happy to fund that development,” he said. “A lot of Web companies would love to start all over and try new concepts and not have the expectations about the delivery of revenue.”

Wouldn’t we all, Mike?

Although expectations, as an old pro like Murphy knows, can certainly cut both ways. In fact, they always do.

Please see this disclosure related to me and Google.