Epic Games, the people behind Bulletstorm, Gears of War, UDK, Infinity Blade, and older Unreal Tournament titles

Epic sent emails to its members of their forums stating that an unauthorized access has occurred into their network and usernames, email addresses, passwords and birthdates may have been accessed by an intruder.  Epic is working on resolving the problem and took their site down while it repairs the breach.

More info from Engadget.com on the hack