It's a really, really big internet. There is room for quite a few more message boards.
ScubaBoard has spawned quite a few scuba-related boards. Instead of feeling insulted, I am honored. Most are allowed to include their URL in their sig line, although there are two sites that are not allowed. To be sure, I have offered help to many of those sites and even give hosting to one site. There is no way that ScubaBoard can fulfill the needs of all of the Scuba Divers, so I encourage competition.
I also sponsor a religious forum, but it was in existence WAY BEFORE I joined here. It is incredibly small, and only a few use it. PM me if you want the URL. If I had more time, I would frequent the other board as well. Alas, I waste most of my time here!