Everyone here is "anonymous" unless they choose to tell their personal details. If Peterb is not your real full legal name then it's no different than posting as anonymous. Davie got it right, though. The board needed posts and drama keeps people coming back for more.
I think the only thing objectionable about posting anonymously is if you are nice under your regular screen name and then post as anonymous to say something you wouldn't say normally. It's funny that some people that object to the anonymous posts use "sock puppets" which you may know is using a second registered name and pretending it is a second identity.
The other funny thing is that one person in this thread has loved and hated me both, when I have posted as anonymous, but would only complain about an anonymous post if they didn't like it. Frankly, why would I bother to create a screen name? So you can form an opinion of me and develop it, think that you like or dislike me based on some posts on a messageboard? Why would you care?