In case you haven't heard by now, Zynga (NASDAQ:ZNGA) is having a bit of an employee retention problem. The social gamer's list of fallen angels is long and growing, including a handful of C-suite execs who have moved on.

That also includes two of the three high-level execs that Zynga had poached from rival Electronic Arts (NASDAQ:EA) in recent years: Jeff Karp and John Schappert. There's still one former EA exec, Barry Cottle, left standing, but more on him later.

Who's the latest chief-something-or-other to call it quits at Zynga?

We have a Wehner!
CFO David Wehner, come on down! Having a CFO call it quits is never a good thing, and of all places, Wehner is leaving to join Facebook (NASDAQ:FB). That could help the social networker gain some additional insight into its growing payments platform, particularly from the perspective of its most important game developer.

Wehner has accepted a senior finance position at Facebook. As part of the switch, three other Zynga execs are seeing their roles expand.

David Ko, who was previously chief mobile officer, has now been promoted to chief operating officer. That was the position that John Schappert had previously occupied, and Ko also spent a decade at Yahoo! (NASDAQ: YHOO) in its mobile business before joining Zynga in October 2010.

Mark Vranesh is now Zynga's CFO, in addition to being its chief accounting officer. This isn't his first rodeo, however, as Vranesh was previously Zynga's CFO from May 2009 to August 2010. Wehner, an investment banker, replaced Vranesh in 2010 in what was an indication that Zynga was on its way to going public. CEO Mark Pincus noted that Wehner helped Zynga's transition from start-up to life in the public fast lane.

Cottle, the final EA alum, is also now chief revenue officer, adding to his role as Zynga's big spender. Cottle has spearheaded Zynga's aggressive acquisition strategy as its leader in business development. Oddly, even though the Cottle had a lot to do with Zynga's acquisition of OMGPOP, which has turned into a combination of reduced guidance, goodwill impairments, and Foolish derision, Cottle's now getting more responsibilities.

It seems like every month, Zynga's management shrinks a little bit more. The exodus began in August, so we're now going on the fourth month of fallout. Who will leave in December?

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