What she said.
Not only does it help compute stats for the forum (which we like to do because it makes our admin's lives easier), but it'll help you keep the player/character roster more organized, and make life easier on you. Even using two groups in the same game in the same forum gets irritating sometimes; ever had a player complain because the thread was getting updated, but now how he/she specifically wanted? It can get under your skin.
Good luck with your games!