Zynga has filed a patent on purchased in-game currency. The company has made hundreds of millions of dollars off of the sale of its in-game currencies.

The patent is specifically for players withdrawing virtual currency for cash and not the other way around; an important distinction since it might otherwise run afoul of certain gambling laws. If granted, this patent may give Zynga extra leverage with Facebook and other social game makers.

Source: VentureBeat