By opening up the Facebook platform for use outside the Facebook domain, the company will create an environment for network effects to propagate. As 3rd parties learn how to leverage the richness of the Facebook data for their own benefit they will become reliant on Facebook. Real businesses will be built using the platform, and Facebook will be able to create new revenue streams in partnership with those businesses. And those revenue streams will drive more value for the company than the ones happening on the facebook.com site itself:
http://www.thestandard.com/news/2008/01/28/facebook-based-apps-can-now-r...