No admin moderation before postings??
Is that your default behaviour?
Because of spam, it a good idee to review alle postings before they released..
Provided that your forum is well frequented: no, it isn't. In that case you are doing nothing else than releasing new entries. The forum script provides several methods of spam prevention. None of them is perfect by itself but in combination they are good enough to prevent overboarding management effort.
Additionally you can restrict the right to post entries to registered users only. You should be able to trust your users and if not, you can disable their accounts.