There was a good article about anonymity vs registration at http://wakaba.c3.cx/shii/shiichan

I want to make an imageboard - not a huge one like 4chan tho. I've started it but it's just something I'm playing with.

I've thought about whether to use registration or not. I don't like having to sign up just to comment on a subject, especially when I don't know if I will come every day and I also don't want the hassle of having to reset my password because I can't remember what I used when I was last logged in 6 months ago.

An idea is, you can give people incentive to come back and post normal / decent content. For example, allow users to post without registration but there are limits such as 15 posts per day or images must not be bigger than 1 Mb. Users can be given the option to create a name and password and build up a reputation. If only they can see their reputation/stats, and they get privilages for producing more posts (without getting banned) then they have an incentive not to shitpost.