Facebook Platform totally went down for around an hour or two because of a buggy release.
The problem was with the JS SDK which is now resolved.
This broke tons of functionality connected to the Facebook Platform all across the web. We believe it affected Facebook powered logins, Facebook Like Buttons, Facebook Comment boxes etc.
With the company just launching their IPO this week, they need to be very careful with stuff like this. Facebook is not just a social network; it is a pretty huge platform that powers a lot of third party services out there!