Actually, it's rather amazing how consistent the actions of Anon tend to be, considering they have no real organization whatsoever.
If the people who attacked Sony claimed to be Anonymous, then they are Anonymous, but since so many members of Anonymous have stated that they had nothing to do with the attack (and probably didn't), at the same time they didn't do it. So they technically did it, but since the majority have distanced themselves from the attacks instead of supporting them, you can't really blame them for the attacks.
In the end, committing your attacks under the label of Anonymous is the perfect plan, because you can say Anon did it, and at the same time no one will blame them. They can't.