Jeff Karp joins chief operating officer John Schappert and chief creative officer Mike Verdu among the top executives who have quit since August.

The world's largest social games maker, which has shed almost three-quarters its market value since a much-heralded debut in December, did not cite a reason for Karp's departure in a filing with the Securities and Exchange Commission on Monday.

"Executive departures are spreading like wildfire at Zynga," said Mike Hickey, an analyst at National Alliance Securities, who has covered the gaming business for about eight years. "I don't think I've ever seen anything like this."

In August, when Zynga shares had already slumped a lot, the company said in a regulatory filing that it was setting aside more stock for employee compensation. The move was likely designed to encourage staff to stick around by replacing under-water stock options with new, lower-priced equity awards. However, departures have continued in recent weeks.

"When you have turnover with the stock already down that suggests a sense of hopelessness within a portion of the employee base," Hickey said. "I don't think business is great. If people were optimistic about future growth, and their compensation is tied to new, lower priced equity, generally they don't leave."

Zynga, which is struggling to staunch growing losses of users, was one of several consumer Internet companies that listed on stock markets to much fanfare in late 2011.

Daily deals purveyor Groupon Inc has lost almost four-fifths its value since its own IPO, which was marred by questions about its accounting practices. On Monday, it named Brian Stevens as its new chief accounting officer.

Zynga reported in July a net loss for its second quarter and cut its full-year earnings per share forecast, news that resulted in shareholder lawsuits against the company.

The company blamed its poor quarter on sudden changes to Facebook's algorithm and delays in its pipeline of new titles.

"Facebook gaming is likely contracting and Zynga is trying to offset that by growing in mobile," Hickey said. "But that inflexion point could be quarters or even years away."

Zynga shares closed 2.1 percent lower at $2.82 on Monday.

Zynga director Reid Hoffman, co-founder and executive chairman of professional network LinkedIn Corp, was asked about Zynga's problems during a TechCrunch conference on Monday.

"They didn't diversify their platform fast enough," Hoffman said. "So when they hit some bumps, the bumps hit them, as opposed to evening it out, whether it's mobile or other kinds of things. The company knows they need to do that."

(Reporting By Alistair Barr and Edwin Chan; Editing by Andre Grenon and Tim Dobbyn)

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