Heh, I have quite a few users that do that (only not nearly to that extent) so it evens out really well for me. Everyone keeps active, and the others post more because everyone else is.
I dunno about the 12 hours a day thing though, that seems like way to much time on the computer. I guess the best thing to do is just let him do it, maybe he'll get sick of it eventually. Or better yet, post more yourself, or encourage others to post more by having contests and rewards for more quality posts.
