How does anyone know that Anon did it?
No one does, and even if a hacker group call themselves Anonymous, that doesn't change anything.
Anonymous, supposedly, has no organization (which is why I facepalmed when the spanish police claimed thay catched 3 ringleaders of Anonymous), stealing doesn't flow with Anonymous ideals.
But anyone can claim to belong to Anonymous, and there's really nothing to that. Blaming Anonymous is as effective as saying "Everyone is guilty!".
The Extra Credits guys say it better than I can.
http://www.escapistmagazine.com/videos/ ... -Anonymous