Did you know Zuckerberg launched a program in July for security researchers, a program that rewards each vulnerability found with a value that, typically, is about $500 per flaw? You didn't know? Neither did I. But I just read an article written by Brian Krebs and, well, now I know it too : )
There really isn't much more to say, so, if this is a topic that interests you, if you want to spend some time hunting for bugs, prepare the saddle and ride to facebook.com/whitehat.
(PS: This is what we really like to do, isn't it? ; ) Good luck!)