From the “and the bug was probably originally named after the Greek god of good intentions” file:
On Monday, we voiced our concerns about the security implications of Facebook’s newly announced messaging service. Today, those concerns take new shape as a Facebook bug has erroneously deactivated a number of accounts on the social networking site.
According to Read Write Web, Facebook has confirmed that a bug that went live today was designed to find and disable accounts that seem fake. The social networking site is apparently working to fix the issue and to get those accounts up and running.