You know on that Groghead site since May 04 48% of the posts were just by two people.
I don't go to many different forums but I have noticed this in the ones I do check out. If it isn't a specialized one, like the BFC forum, most of the action seems to be started by a small number of people. A great example is the Political forum on dosomefink. It can be a very active place but when Dirtweasel doesn't post for a few days, all discussion seems to stop. Most of the posters there share his political point of view but when he isn't posting the conversations dry up quickly. Dorosh runs away and the people that post in agreement with him or dissention, have nothing to riff off of.
NUTT recently started a thread that I thought was very interesting and fun to read, regarding flamethrowers. I just didn't know how to comment on it. I suppose I should have at least said "thanks.....that was a cool read".