The content-discovery service, StumbleUpon, has gotten itself back to start-up status, after being bought by eBay two years ago.

It announced today that it was returning to being an “investor-backed startup” by a roster of well-known Silicon Valley investors, including Ram Shriram of Sherpalo Ventures, Accel Partners and August Capital.

Its founders, Garrett Camp and Geoff Smith are also back, with Camp now in place as CEO.

“We are grateful to eBay for its guidance. However, we realized there were few long-term synergies between the two businesses. It is best for us to part ways and focus on our respective strengths,” said Camp, stating the very obvious.

That’s quite a boomerang since it was acquired by the auction giant in 2007 for $75 million.

Before that event, which was at the height of the Web 2.0 fervor, the Canadian-born social-bookmarking start-up, which launched several years ago, came to the Bay area in 2006 and got some fancy venture investors (Mitch Kapor, Ron Conway, Shriram and others) who ponied up a couple of million dollars. It soon became a traffic-generating hit.

But rumors of the San Francisco-based company being sold by eBay (EBAY) have swirled around it almost since it was bought, although there was no sale.

The same has been true for eBay’s other purchase, of voice-over-IP service Skype. A recent report in the New York Times said its founders were also considering buying Skype back from eBay.

Under eBay, the site has floundered a little bit, but made some changes, such as unveiling a new Web-centric look and feel and a new partnering program last fall that represented a major shift for the online discovery service.

In that change, users no longer had to register for the service or download its toolbar to “stumble” the Web.

Terms of the deal were not released, but we’re digging! Um, stumbling!

More to come, but here’s the full press release from the company, as well as a video I did at the party StumbleUpon threw after getting acquired by eBay, including an interview with then-thrilled Camp:

StumbleUpon Goes Independent; Backed by Founders and New Investors

April 13, 2009 – StumbleUpon, the best way to discover new content on the Internet, today announced that after nearly 2 years as a subsidiary of eBay Inc., it has returned to the ranks of an investor-backed startup. StumbleUpon is now backed by the original company founders, Garrett Camp and Geoff Smith, as well as a number of well-known investors including Ram Shriram of Sherpalo Ventures, Accel Partners, and August Capital. Camp takes on the role of CEO of StumbleUpon.

“We are grateful to eBay for its guidance. However, we realized there were few long-term synergies between the two businesses. It is best for us to part ways and focus on our respective strengths,” said Camp. “This change makes it possible for StumbleUpon to continue to innovate and focus on becoming the Web’s largest recommendation service.”

“StumbleUpon helps users discover the best of the web–it’s a way to find interesting content you wouldn’t think to search for,” said Shriram. “StumbleUpon’s personalized recommendation engine brings serendipity back to websurfing, and lets users sift through socially-endorsed content with a single click.”

StumbleUpon will remain focused on helping people discover interesting content by increasing the accessibility of the StumbleUpon service and the quality of recommendations. In addition, StumbleUpon has plans for several new products and features to be released in the upcoming months.

And, no surprise, he is the No. 1 choice of most inside and outside Yahoo (YHOO) in the wake of the news late yesterday that current CEO and Co-Founder Jerry Yang is stepping down.

And why not? Chernin has the right resume: Experienced at running large and complex organizations; savvier than most in media about the Internet; able to make the kinds of dramatic decisions needed; and, perhaps best of all, signaling–via the Los Angeles Times–just this past week that he was open to leaving the powerful media and entertainment conglomerate for something new.

Well, Yahoo would certainly be new for Chernin, in terms of a corporate cleanup challenge, especially compared to figuring out how to make bank on plush toys from “The Simpsons.”

And, while the risks are many, if Chernin (pictured here) managed to turn around Yahoo, he could make a huge fortune too, given Yahoo shares have languished of late, much in the same way they did when former CEO Terry Semel came to Yahoo from Hollywood in 2001.

But it’s not altogether clear whether Chernin would actually leave his powerful perch at News Corp. (NWS)–which owns Dow Jones and owns this Web site. He has been ensconced there for a dozen years, building a huge reputation as a sharp exec (No, Peter, I am not kissing up, as I think Yahoo would wear even you down very, very quickly).

That’s even though many note he is not likely to take over as CEO from its iconic leader, Rupert Murdoch. The media mogul is widely expected to favor one of his own children to lead News Corp. next.

And the 57-year-old Chernin already makes close to $30 million in his current job, which is definitely challenging.

And, although Chernin has been involved in the News Corp.-owned MySpace and has had success backing the Hulu online video site, it is not nearly as hard as the five-year turnaround quagmire (plus no fabulous media mogul perks either) that Yahoo could turn out to be.

In addition, privately to other News Corp. execs, Chernin has regularly pooh-poohed a move to a digital company, even though he is always on the short list for a lot of big Internet jobs–such as the long-unfilled post as digital head at Microsoft (MSFT) more recently.

So, who else to take over from Yang, who will return to his job as Chief Yahoo after stepping down from the company as soon a search for a replacement CEO is successful?

Well, here is BoomTown’s own shortish list, based on asking a wide range of people inside and outside Yahoo, all of whom are important digital players in their own right.

INSIDE YAHOO

Sue Decker:

The current President of Yahoo is certainly being “considered” for the job, which is a polite term for not really being considered at all. While Decker is an intelligent and thoughtful exec, like a politician with a record, she has had her hand on the operating tiller at Yahoo for too long not to get deservedly blamed for its current situation.

In addition, she is radioactive to big investors, who have told the Yahoo board in no uncertain terms that she is a nonstarter.

Maggie Wilderotter:

The former Microsoft exec, who has also been a public company CEO, is an interesting idea floated by some, who think the Yahoo board might turn to one of its own directors, as a short-term solution to stabilize Yahoo.

Wilderotter has been much focused, said several Yahoo execs, on cost-cutting at Yahoo and certainly is not as tarnished, being a more current board member. But she is a largely unknown quantity in the Internet space and, most importantly, at Yahoo.

John Chapple:

The former CEO of Nextel is one of the two board members (former media Frank Biondi Jr. is the other) recently picked by Carl Icahn, when the activist shareholder was admitted on the board as part of the proxy fight settlement.

Chapple has, sources said, been conducting chats with Yahoo execs lately, perhaps as a way to get a lay of the land. If he got the job, it would be clear Icahn had won his Pyrrhic victory (and personal financial defeat) against Yang.

OUTSIDE YAHOO

Dan Rosensweig:

The very funny, but brash, former Yahoo COO is definitely a favorite within Yahoo’s ranks, except for those who don’t like him. But it’s clear Rosensweig does know and love Yahoo, is close to Yang and, ironically, enjoys a tight relationship with Microsoft CEO Steve Ballmer, who also wanted him for the digital head job.

Also, Rosensweig, who does have operating chops, has gotten some much needed time away from Yahoo, as a partner at the tony media investment firm, the Quadrangle Group.

Meg Whitman:

Another dreamy CEO choice, except she has already been a big company CEO at eBay (EBAY), has proved her mettle in building it to a powerhouse–despite the online auction site’s currently harder times–and has the giant fortune to prove it.

And, oh yes, she is likely to be using that pile of cash to run for governor of California, on the Republican ticket.

Jon Miller/Ross Levinsohn:

The Bobbsey Twins of the Internet, the pair are now having a very good time running their own investment company, the Velocity Group.

But, aside from some questioning whether he can make the quick decisions needed at Yahoo, Miller (pictured here on the right), the former head of AOL, does not want to leave his New York home and cannot take any job anyway until his noncompete with Time Warner (TWX) runs out in March.

And former Fox Interactive Media head Levinsohn likes Los Angeles, and probably is too fast a personality for Yahoo (his going there would be a shock to its system, but would be endlessly entertaining to me personally).

Tim Armstrong:

The top ad exec at Google (GOOG) certainly is an interesting idea, although has little of the product experience needed to run Yahoo. But he is a well-respected advertising figure–where Yahoo needs to shine–and could do well with a lot of strong execs under him.

He is also not on a CEO path at Google–paging, Larry Page!–and could be interested in proving he could run a company on his own.

Kevin Johnson:

The former Microsoft exec was supposed to be running Yahoo, if he and Ballmer pulled off their takeover attempt earlier this year. They did not, and Johnson then left Microsoft to run Juniper Networks (JNPR) in Silicon Valley, right up the road from Yahoo, in fact.

But Johnson is likely subject to a noncompete by Microsoft and a strong contract at Juniper too. Still, a very sharp exec, he definitely has the operating, political, technological and digital skills to take on Yahoo. Also, ironically, he and Yang really get along well and like each other, despite the takeover battle.

Of course, there are a lot of other ideas: Disney (DIS) online exec Steve Wadsworth; the outside-the-box choice of former Procter & Gamble (PG) marketing wizard Jim Stengel; Microsoft digital exec Yusuf Mehdi; CBS (CBS) digital head Quincy Smith (whose hyperactive dealmaking would likely lead to a mutant merger between CBS and Yahoo); and former Cisco (CSCO) and current Joost CEO Mike Volpi.

Please post suggestions below or, better yet, send tips to me at here.

Please see this disclosure related to me and Google.

In the late 1990s, during the height of the bubble of Web 1.0, there was a poolside charity auction at an Industry Standard conference for a variety of items donated by Web luminaries.

A tie from John Doerr, the right to push eBay CEO Meg Whitman in the pool and also the little black dress that then-CEO Katrina Garnett of CrossWorlds Software had worn and made famous in a Richard Avedon-shot ad for the company.

I am blanking on the person who bought the dress, but what was most interesting about that item was that the same person kept upping his own price, and went several rounds bidding against himself before winning the prize for a lot of money.

It was amusing at the time, a symbol of a very frothy time indeed.

Today is not that time, so I was a bit perplexed at why Microsoft (MSFT) would top its own bid and raise its $31-per-share offer for Yahoo (YHOO) to $34 a share, as suggested by Citigroup (C) analyst Mark Mahaney yesterday.

There seem to be no other rivals and not much has changed since the software giant made its unsolicited offer at the start of February, except for time passing.

Of course, the only reason to do so then is to get the deal done sooner than later and perhaps the number was a public message to Microsoft CEO Steve Ballmer of that fact (as I said before, I am sure there are plenty of private messages too).

And while I am in the camp that Yahoo, well run, is probably worth a whole lot more (see this post I did at the start of this slog) than even $34–although perhaps not the $40 that Yahoo claimed last week–it’s still a matter of actually getting Microsoft to pay it by bidding against itself.

As I saw back in the roaring ’90s, it could happen. The question is: What will it take to get Microsoft to do it?

My guess if it happens: Sheer boredom and the cost of wasted time during which rival Google (GOOG) keeps chugging along and a distracted Microsoft and Yahoo do not.

Please see this disclosure related to me and Google.