Yahoo has hired a new head of mergers and acquisitions–former General Electric (GE) M&A exec Andrew Siegel, who will now be VP of corporate development.

Yahoo (YHOO) CFO Tim Morse dropped the news with exactly no details about that title in an interview with The Wall Street Journal about the Silicon Valley Internet giant’s third-quarter earnings.

Another question apparently not answered was what exactly is the status of its current top M&A exec, Greg Mrva–who has had the title Siegel has now posted on his LinkedIn profile–as well as that of VP of mergers and acquisitions more recently.

In other words: Where the heck is Greg?

BoomTown was considering a search party–get it?–if Yahoo hadn’t outsourced that to Microsoft (MSFT). Thus, Plan B: Mrva milk cartons!

On Facebook, Mrva is still listed as being in the Yahoo network, although there was a report floated recently by Silicon Alley Insider that he was asked by Morse to leave his M&A job at Yahoo and find a new one at the company.

Whatever the situation–either Mrva running it with Siegel or being hipchecked out by him–helming M&A at Yahoo can’t be a fun job right now, given that the company has been looking to sell quite a few of its assets, including its Zimbra open-source email business, its personals unit, its HotJobs online classified business and many more to come, said sources.

In fact, in a recent post, BoomTown wrote: “Mrva’s new job title should be: VP of un-mergers and de-acquisitions.”

The effort to unload big swathes of Yahoo is part of an aim by new management to slim down its diverse portfolio, even as it strives to redefine itself with a new, pricey marketing campaign that seeks to position the company primarily as a consumer offering.

Mrva has been the main exec shopping Yahoo properties around, according to many sources, a job that will now apparently be Siegel’s.

Yahoo CEO Carol Bartz has said the company is also looking for acquisitions, mostly small, so perhaps there will be more to do for the company’s dealmakers than running an Internet garage sale.

I contacted Yahoo to find out what’s up with Siegel and Mrva, a well-liked exec in Silicon Valley, and also have reached out to him. When either responds with anything of note, I will update here.

According to numerous sources, Yahoo has been shopping around Zimbra, the open-source email company it bought in late 2007 for $350 million.

Zimbra is only one of the many assets of Yahoo (YHOO) that are now on the block, including its personals business, its HotJobs online classified unit and many more to come, said sources.

The effort to unload Zimbra is yet another sign that the company is trying to slim down its diverse portfolio, even as it strives to redefine itself this week with a new, pricey marketing campaign that seeks to position Yahoo primarily as a consumer company.

As first reported by BoomTown last week, Yahoo will be introducing a massive branding campaign tomorrow on the second day of Advertising Week in New York.

The new focus Yahoo is aiming for with advertisers is to stress its huge size and scale with consumers. The troubled Internet giant is still one of the most trafficked sites on the Web.

And consumers will also be reminded of this. The Wall Street Journal wrote a follow-up story yesterday on the marketing effort, noting that the $100 million campaign’s tagline is “It’s You.”

Get it? The “Y” in Yahoo is the same as the one in You!

The details of the plan will be made public tomorrow at a press conference immediately after a keynote speech–titled “Yahoo’s Consumer Revolution…Round II”–that the company’s new CMO, Elisa Steele, is set to deliver at the Interactive Advertising Bureau’s MIXX conference.

The goal, said several sources at Yahoo, will be to stress Yahoo’s consumer business over all others, which are supported mostly via brand advertising, leaving more extraneous ones out in the cold.

Which is why Zimbra–like a lot of other Yahoo properties–is being shopped around by its top mergers and acquisitions exec, Greg Mrva and others.

(Mrva’s new job title should be: VP of un-mergers and de-acquisitions.)

Backed by Benchmark Capital, Redpoint Ventures and Accel Partners, Zimbra was an innovative start-up whose main business was to provide clients–including Comcast (CMCSA), many ISPs and a number of colleges–with white-label email software capabilities.

Yahoo bought the company to goose that business, whose main rival has been Google (GOOG)–along with using Zimbra technology to improve its massive consumer email offering, also under siege from Google.

That integration has gone slowly, and Yahoo now has less interest in selling email products to others.

But the price Yahoo would get, many think, would be significantly lower that what it paid for Zimbra.

Nonetheless, potential buyers include Comcast and Google, as well as private-equity investors.

In addition, it is not out of the question that its former venture investors could be interested in a classic Silicon Valley buyback.

Zimbra’s founder and CEO, Satish Dharmaraj, who left Yahoo earlier this year, is now working at Redpoint.

Here is a video interview I did with Dharmaraj in early 2008, after the Yahoo deal was struck:

Last week–in a clear sign that BoomTown has spent way too much face time in front of the idiot box–I compared the endless bickering back-and-forth between Yahoo CEO Jerry Yang and Microsoft CEO Steve Ballmer to the annoying push-me-pull-you antics of Ross and Rachel on the television show, “Friends.”

But the continuing discussions between Yahoo and AOL execs over the merger of their struggling online companies have their own TV comparison–the never-ending roundelay on “The View.”

In other words: Blah, blah, blah. Chitter-chatter. Pointless arguing. Chin-scratching. More blah, blah. More chatter. Blah.

Thus, there were still more discussions going on at Yahoo HQ this past week about the possible deal, in which Yahoo is code-named Yale and AOL Amherst.

Along with Yahoo CEO Jerry Yang and President Sue Decker, the key Yahoo (YHOO) execs involved in pushing forward the effort, are U.S. head Hilary Schneider, and Greg Mrva, a former investment banker and analyst who is in charge of mergers and acquisitions at the company.

As I previously wrote, the main suits involved in repping the Time Warner (TWX) unit are AOL President Ron Grant and Time Warner M&A SVP Jim Burtson.

“More of the same discussions about how it would all integrate,” said one source close to the situation at Yahoo. “Same as always.”

Added an AOL source, in what I consider the understatement of the year: “There has not been a lot of clarity in decision-making at Yahoo.”

Big surprise: Still no deal!

That’s unusual to me, since all the true obstacles–namely, the collapse of the controversial search advertising deal Yahoo tried to strike with Google (GOOG), AOL and Yahoo’s results coming in as weak as expected and, lastly, a definite lack of interest from Microsoft (MSFT) to rebid for Yahoo–are no longer in the way.

And, of course, Yahoo’s share price–the stock has settled into the depressing $11 to $12 range that gives the company a $15.7 billion valuation–is simply not going up any time soon.

So, if the deal is to be done, the price–or percentage, really–will probably have to be based on today’s reality, which is a very bleak outlook in the graphical online advertising business in which Yahoo plays most strongly.

That’s why dithering is a problem for this possible marriage, despite all the obvious complexity.

For one, it takes all the air out of any momentum such a combination could produce for either Yahoo or AOL, which will be much needed in the current economic environment.

In fact, such an econalypse is actually the perfect cover to try to pull this turnaround–and it is exactly that–off, given few investors or media will expect much from the merger for a while and be more forgiving.

In addition, the slash-and-burn integration needed to drastically refocus the new company–hopefully on three things only: advertising, content and communications–will be easier now more than later when the financial outlook improves.

“Things are going to get a lot worse than people think,” said one AOL exec. “So, this is a really good time for a reset and for cleaning things up.”

It is also easier now to bring in fresh ideas and new leadership to a combined Yahoo/AOL, as a new company will surely give many talented outside execs who have avoided both separately a reason to look again.

I could go on as to why this deal should move forward quickly, but here is one piece of great advice I got several years ago, from a well-known Internet entrepreneur whose company had just taken a big gamble by buying a controversial but fast-growing start-up in a key category.

At the time, many decried the move as too risky and too pricey and too thoughtlessly done. When I asked the exec about this, he did not argue, but offered this:

“No one really knows how anything is going to turn out, no matter how long they think it through,” he said. “But, I believe it will all work out if we execute well on the promise, because I did know one thing for sure: It was the right direction.”

And, indeed, while you can puzzle over a map endlessly, knowing the right direction to go in is the only thing one can be sure of in almost any circumstance in life.

Therefore, all Yahoo and AOL have to do is pick a path–whether it be to move on or merge–and just go.

By tomorrow would work for me.

In the meantime, below is a video I did of Yahoo’s Yang onstage at the Web 2.0 Summit in San Francisco last week, talking about the travails of the last year.

It includes him saying Microsoft should still buy Yahoo, which felt a little too much like a plea to me. (I happened to be sitting next to some Microsoft execs during the speech and they did not look too moved by the begging.)

But judge for yourself–here’s the video (yes, the Web 2.0 Summit organizers did flash a picture of a jar of Jif peanut butter as a joke–ha, ha, referring to the infamous Yahoo “Peanut Butter Manifesto”):