One-upping the much-buzzed about “MySpace ecosystem,” college-based social network Facebook has opened up its API to outside developers. (Thanks Marc!)
A discussion board is already buzzing with ideas for Facebook widgets and mashups, including address book and music service integration, chatrooms, and textbook sales. The only live application so far is a social money-tracking service called FaceBank, which is similar to BillMonk. (You may not be able to access all this if you are not registered with Facebook…I had to authenticate more than once.)

Facebook is limiting requests to 100,000 per hour for web apps and five per second per user of desktop apps. The API is currently available for free but Facebook reserves the right to charge.
Integrating social networks is sure to be increasingly important as teens tire of checking their MySpace, Facebook, Bebo, Tagged, TagWorld, et cetera, accounts every day. In another cooperative move, XuQa, which we wrote about earlier today, is letting people import their MySpace profiles wholesale. MySpace, on the other hand, has been pushing users to upgrade their Flash, forcing some widget-makers to figure out another way to grow virally.