Facebook began testing its virtual currency, called Credits, more than a year ago with some popular games on Facebook. This month, Credits passed a milestone when it became the exclusive payment method for most of the games created by Zynga, the No. 1 developer of Facebook applications.
Zynga is expected to have $500 million in revenue this year, according to the Inside Network, which tracks Facebook applications, as millions of users pay real money to buy virtual goods on games like FarmVille and Mafia Wars. Through Credits, Facebook will take a 30 percent cut.
By the end of the year, Facebook expects that Credits will be used to buy the vast majority of virtual goods sold on Facebook.