According to this new post on the SitePoint blog, you could win some cash if your Facebook application is chosen as best:

Our current feature article about developing for the Facebook Platform with PHP is extraordinarily timely, given the recent announcement from venture capital firm Bay Partners on Tuesday that they will be offering cash prizes for the best Facebook applications.

According to the article, Bay Partners will be offering cash awards (ranging from $25,000 up to $250,000) for the best applications built on top of the Facebook API. You can get more information about this AppFactory program from the Bay Partners website (as well as how to apply for the contest).