'FarmVille'

Zynga, the makers of 'FarmVille' and 'Mafia Wars' has been seeing many dollar signs lately. On almost any day 500,000 tractors are sold to the around 50 million players of FarmVille, the largest and fastest growing social game on the Internet. Annual revenue at the two-year-old firm is likely to pass $100 million this year, prompting speculation that the company (backed by the likes of Linkedln cofounder Reid Hoffman and PayPal cofounder-turned-investor Peter Thiel) will soon go public. The software company also has managed to do something that other popular sites such as Twitter and Facebook have not: Zynga has found a way to make social networking profitable.

This company was founded in 2007 by Mark Pincus, 43, who also started social-networking site Tribe.net and software company SupportSoft (SPRT), which eventually went public. Most of his Web 3.0 peers rely on advertising and sponsorship for revenue, Picnus makes its money by getting gamers to buy virtual goods, like tractor fuel or land in FarmVille, which enable players to build bigger farms at a faster rate. Once hooked, Pincus says, players spend real money on virtual goods to help them advance to higher levels.