Right now, a majority of active old users have their posts in MSG.
Granted, I haven't been around enough to actually participate a bunch of games that have been sent there, but I feel that the post count gets really bloated when at least a quarter are in those subforums alone.
Stats-wise, A quarter of my posts are in RPG, and TARC, HME, TSC, and MSG are the top 4 afterwards.
Compare to the idlebot Dormio, who has about two-thirds of his/her posts in MSG and RPG alone.