Facebook is growing 3% per week currently (6th most trafficked site in the U.S.). I guess it will not be long before Facebook would catch Myspace traffic and leave it behind. A week ago (05/24/2007) Facebook launched Facebook Platform - giving away the Facebook API and the ability to integrate 3rd parties applications into their website.
I'm a bit late on it since a bunch of companies including Microsoft, Amazon, Slide, etc had developed prototypes and even production-level applications to integrate.
I've made a bit of reverse engineering through Facebook business entities and created a class diagram - on the screenshot below (clickable)
Saturday, June 02, 2007 5:47 AM