The gaming company behind Facebook's popular Farmville and Mafia Wars filed an initial public offering on Friday, joining a host of other social media companies who have gone public this year. Zynga's IPO could raise up to $2 billion, a source says, valuing the company at $15 to $20 billion. Together, Farmvile and Mafia Wars have 232 million active monthly users. By tapping into Facebook as a platform that doesn't require hardware like PlayStation or Wii, Zynga has carved out a new position in the video game industry, making it extremely appealing to investors.
