On any given day 500,000 virtual tractors are sold at $20 a pop. Who would do such a thing? The 50 million players of FarmVille, the largest and fastest-growing social game on the Internet, do.

Social games are free online applications accessed through sites such as MySpace and Facebook. FarmVille, Mafia Wars, and Caf World all currently rank in the top five most-played of these titles, and all three were developed by San Francisco-based Zynga.

Annual revenue at the two-year-old firm is likely to surpass $100 million this year, prompting speculation that the company will soon go public. The software company also has managed to do something that other hot online brands such as Twitter and Facebook have not: Zynga has found a way to make social networking profitable. By developing games on social networks, Zynga is able to capitalize on the viral nature of the platform. Once hooked, players spend real money on virtual goods to help them advance to higher levels, and although playing requires only short spurts of time, the game never ends.

Calling all FarmVille players! Come on out of the barn and share your experiences below!

Source: CNN