At the moment, it is possible for someone to post here without registering. They post as "Guest." The problem is that a lot of people who are registered wind up posting as "Guest" because they forget to sign in. Because a "Guest" post can't be modified, if you make a mistake on one of those posts you can't go back and fix it or delete it.
My suggestion is to do what most other bulletin boards do and force registration/login prior to posting. I don't think it would do any injustice, i.e., strip away anonymity, because just about everyone uses a pseudonym when they register.