Everyone's been wondering what the Facebook's business model will be. Despite assumptions that the website will rely on advertising, the social networking site is hard at work developing a virtual currency system that will involve real dollars, and hence real revenue for Facebook.

The idea is that 10 Facebook credits would cost a dollar, and users could buy them or get them from advertisers. Those credits could be traded among users or used to buy applications. Facebook is now testing the system with a couple of applications, and we should hear more about it in the next few weeks.