Zynga's stock plunges as founder's return as CEO brings back bad memories for investors

The return of Zynga founder Mark Pincus as the digital game maker's CEO is bring back bad memories about the problems that prompted him to step down as the company's leader nearly two years ago.

Zynga's stock shed 43 cents, or nearly 15 percent, to $2.47 in Thursday's trading as investors reacted to an abrupt change in command announced late Wednesday.

Don Mattrick, a former Microsoft executive recruited to clean up a mess that Pincus helped create, resigned as CEO, effective immediately. Pincus, Zynga's controlling shareholder, moved back into the CEO job.

With Pincus at the helm, Zynga lost more than $600 million in 2011 and 2012 as once-trendy games like "FarmVille" fell out of favor. The downturn also battered Zynga's stock, pressuring Pincus to get help from a new CEO.