Anime bulletin boards? You mean those comics from Japan, where everyone has huge eyes? I've only seen a couple in my 15 years on the Internet. I'd imagine that a niche like that is ... well, about as rare as talk shows hosted by rabid right wingers on AM radio stations in the United States.
I'd imagine that the only thing that's harder to find is a vBulletin site dedicated to perhaps the most esoteric topic out there ... first person shooter PC games.