Value of IPO: $1 billion
First day of trading: December 15, 2011
Market status: Active
The developer of "Mafia Wars" is also the don of video game IPOs. Still, that's little consolation for investors, who have watched the San Francisco-based social gaming company's stock plummet about 50 percent since its market debut.
Zynga, which also produces "CityVille" and "FarmVille," did see its stock jump in January after the company said it would cut 15 percent of its staff and buy mobile developer NaturalMotion for $527 million.
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