There is a bad design in the message-post page in forums that you will want to check out before the site goes live. I've meant to post my corrections to the page in the sdm, but haven't had time to make the changes to the latest cvs version.
Among other problems which don't use the form-templating correctly, the most critical problem is that the command:
set message_id [db_nextval acs_object_id_seq]
is called with each page request. If I don't actually post a message, but just reload the page over and over, I increment the sequence.
Anyway, thought I'd give you the heads up.