Preserving Security By Buying Stolen Passwords

Nice article from Gizmodo explaining how Facebook protects its users by prowling the Black Market for stolen credentials. These stolen passwords are then compared against it's user database to determine if existing users have compromised credentials.

This proactive step allows Facebook to warn users who are often unaware that they have had accounts hacked and information leaked even if the origin of the outbreak was from another service. Its a grey area but I am happy that companies are willing to take a risk to preserve security.