I joined a Stephen King discussion board a few years back and had that very thing happen to me. I sent a PM to the administrator and she said they went through a time where people were posting insulting things about King and passing on information that was completely wrong, starting nasty rumors and such. Having a moderator approve every post was their solution to that problem, which I told them totally sucked. Particularly when there is ONE moderator on the board. If she wasn't logged in your posts didn't go up. Stupid idea. Totally stupid.
I was bummed that I couldn't join the place as big a Stephen King fan as I am, but regardless, I would not put up with that crap. I was surprised there were so many regular members there! They had something like 700 members. I am not among that number any longer, obviously.