I think it needs to be said again and again: Anonymous is just A CONCEPT! The group that are calling themselves Anonymous are mostly made up of 4chan trolls.
Just like many concepts, Anonymous is neither Good or Evil, it's just neutral. A quote from wikipedia
Anonymous (used as a mass noun) is an Internet meme that originated in 2003 on the imageboard 4chan, representing the concept of many online and offline community users simultaneously existing as an anarchic, digitized global brain.
To put it simply, you can't put a 'Good' or 'Evil' tag on them. The only thing that binds them is just that they just do whatever the hell they wanna do regardless of morals and reason.
In the end, it's their action that counts so it's up to you whether or not to support they're action because you might not know it but 'You are also part of the Anonymous if you're using the Internet' and every post you make on the Internet influences the Anonymous' (as a whole) action.