Actually ichigo, my idea was having a joinable usergroup. Having X amount of posts is a pain and just gives people a reasion to spam. I'll come on the IRC after school and explain this 'joinable usergroups' idea further.
But in a nutshell, joinable usergroups can have an appointed usergroup leader, they can accept or decline incoming join requests. I have a good amount of experience with vBulliten, and for the things I don't know, I have hundreds of people to ask.
Here is an example.
http://www.mark-3halo.com/m3hforum/showthread.php?t=14