two "veteran" members of Anonymous say some element of the organization was "likely" behind the attacks on Sony earlier this month. At least, they're saying that as much as any two people can take credit for a large, essentially unconnected group of strangers. There was an "official" Anonymous movement against Sony called "OpSony," say the veteran members, and according to them, "if you say you are Anonymous, and do something as Anonymous, then Anonymous did it."
That's the problem Sony is having with the non-organization -- members of Anonymous have both now taken credit for and denied being behind the attacks, but since Anonymous is by definition a decentralized, self-defined community, it can't really "take credit" or be held responsible for anything itself.
That said, while the Anonymous movement is hard to pin down, it is made up of a group of real people, and those people are being investigated as "one of the key targets" by US law enforcement. If and when charges are brought in this case, "Anonymous" won't be on the stand -- it's not a real organization you can arrest or subpoena. But the hackers who were reportedly acting in conjunction with the online movement likely will be.