Anonymous is an internet bogeyman - and it is by being anonymous that they have their greatest strength and their greatest weakness.
Anybody can say they were attacked by Anonymous, and how would Anonymous be able to know? The closest you have is there are two primary methods for discussion related to Anonymous - their Press Release website and their IRC chatroom, AnonOps. This is the organization of Anonymous.
The current hate is because of Sony and the PSN - but who's to say that it is Anonymous or a splinter group from Anonymous? Why can't it be Sony causing the PSN to go down - attacks by Anonymous will create a different reaction than having to go down because of maintainance or some other issue of negligence.
Then there is always the issue that it might be a member of Anonymous within Sony themselves - they would have the best experience on how to take down PSN from the inside, and can keep it down simply by stalling over how to fix it.
We don't know, and may never know. The people telling us have reasons to lie and bias the truth.
It doesn't really matter - if anything, the loss of PSN is comparable to why GeoHotz jailbreaked the PS3, and Anonymous attacked Sony in the first place - it's the removal of a service that people bought the PS3 for, without regard. Of course Sony are going to blame Anonymous, because what would the backlash be for Sony if they had to admit it was actually their own fault - or worse, they actually chose to remove it. Now all PS3 users can feel the same as the ones who originally lost out. Few people care about things unless it affects them - now it's affecting them, and now they care.
Anyone with a slight amount of intellect and independent thought can see what is really going on. Everyone else will just believe whatever bull is fed to them by whatever side they associate with most, and for the majority of gamers, this is going to be Sony.