Breakout Companies of 2010

Courtesy Company
7 of 11

San Francisco
Founded in 2007

Why they’re on the list: For earning a $5 billion valuation

The popularity of Facebook continues to soar at least in part because of companies like Zynga, the software maker that has become one of the leading developers of social networking games. Fueled by the massive popularity of its games like FarmVille and Mafia Wars, which users pay fees to play, Zynga, which boasts some 320 million registered users, has seen its revenues skyrocket to a reported $500 million a year – leading analysts to value the company at about $5 billion. The company has also gone on an acquisition spree in the past year, fueled by capital supplied by high-profile investors Softbank and Google.