Personally I’d be wary of hosting anonymous posts, due to the guaranteed spam-tidal-wave that would eventually arrive, but I know people who share your justified lazyness regarding the frighteningly bureaucratic “registering”.
Currently, bbPress is built so that all users must be registered to post. I have heard talk of a plugin for anonymous posting, but nothing in development to my understanding.
So far, registration on the bbPress side is wide open, but if you are integrated with WordPress there are hacks in WordPress to have admin approval for registration, but only if you change all registration for the forums to the WordPress side versus bbPress.
It can’t be done yet, but I think it was in a discussion on trac that the devs were discussing this, and the plan is to change core files so that a plugin can make it possible. It just won’t be until 1.0 or later is released, sorry.
i had a look at code trying to do something in this way, but i wasn’t able to find the right function to hook… i can find the pre_post_form and post_form, this one allows me to work only after the post form so i think that in this very moment there is no way to do it, or better there is no way using a plugin…