Zynga (Nasdaq: ZNGA), the largest maker of games played on social networks, said Chief Financial Officer David Wehner is departing to take a senior finance job at Facebook Inc. He’ll be succeeded by Mark Vranesh.

Chief Mobile Officer David Ko was named chief operations officer, while Barry Cottle was appointed chief revenue officer and Steven Chiang became president of games, San Francisco-based Zynga said Tuesday in a statement.

Wehner’s departure less than a year after the company’s initial public offering – and following the exits of at least eight other senior managers since August – weakens confidence in Zynga’s turnaround efforts. Chief Executive Officer Mark Pincus has embarked on a restructuring aimed at cutting costs and boosting revenue from games on mobile devices.

“When executives start voting with their feet, it sends a more powerful message than anything the company can say,” said Arvind Bhatia, an analyst at Sterne Agee & Leach Inc. in Dallas, who has a neutral rating on the stock. “It seems more and more that the company is going to have continued issues.”

Zynga reiterated the financial forecast it gave last month, when it said 2012 bookings, a predictor of sales, will be $1.09 billion to $1.1 billion. It also said full-year per-share profit, excluding some costs, will be 2 cents to 3 cents, not including the effect of share repurchases.
Wehner will become Facebook’s vice president of corporate finance and business planning, Ashley Zandy, a spokeswoman for the Menlo Park, California-based social network, said in a statement yesterday.

Keeping Talent

Pincus is struggling to retain some top deputies as a plummeting stock price — it has declined 79 percent since the December IPO — erodes the value of equity-based compensation. Jeff Karp, Zynga’s former marketing chief, resigned in September, following the departures of former COO John Schappert and former chief creative officer Mike Verdu.

The company is cutting 5 percent of staff, shutting offices and ending more than a dozen titles, Pincus told employees in a memo last month.

Vranesh previously served as Zynga’s CFO before he became chief accounting officer in 2010.

The latest changes elevate Ko, a former Yahoo! Inc. executive who joined the game maker in 2010 and oversaw the creation of more than 25 titles for mobile devices. He now oversees all strategy, planning and operations at Zynga, according to the company’s website.

Zynga was little changed at $2.11 at Tuesday’s close in New York, prior to the announcement of management changes.