Seems like this comes up periodically, and the answer is to maintain two boards. This one where new members come in, and another private, invitation only board. Say only folks who hit a Monkinar get approved. The difficulty comes in where you have a whole lot of people trying to keep stuff under wraps, someone would wind up posting something on the public board that needed to stay private. Mods would have to be sharp on the public board to keep the secret stuff secret.