An Facebook app call Photo of the Day :
demostrated a PoC of how Facebook can DoS another site. This app basically in short show 1 photos from National Geographic. But downloads 3 more huge files from somewhere else. Or for that matters, you can do upload, posts, requests or whatever you can imagine using hte Facebook API. Effectively, all you need is millions of people to sign up your app, then when they log in, they become your botnet to DoS someone.
For example, I can up my site counter to millions easily by creating a bogus app that gives free paypal money when you refer someone. Of course on the side line, I can con some paypal accounts as well. :) Then I can make a hidden read to my site in the app and not disaply it. Once millions sign up, millions will visit my site. OK, shake this off your head. This is a (C)Copyright idea... Hahaha. Seriously, its that simple. Make you wonder why it hasn't happen yet. (Or is has... We just did not hear of it)
Anyway, here is the full whitepaper :