The BTS has disappeared. Actually, it happened about a month ago, but I never overcame the lack of caring enough to poke around and find out why, even though I read the list, for my own amusement. (I don't know why watching people use anonymity to act like cranky 12 year olds with big thesaurii amused me, but it did. Also, always looking for my own name, because I'm always willing to believe I've written crap, and I'm always willing to be offended by people saying that things I know *aren't* crap, are.)
Finally found the one message that they (the official BTS members, as opposed to those of us on the mailing list, who varied from lurkers to occasional commenters, to slingers of outright viciousness that should make the original squad proud) left to announce their mysterious disappearance.
I think I understand. They disliked the fact that they'd opened up their small society of muckspitters to people who would ask them to back up their assertions with honest discussion of what bothered them in the fanfics they skewer. They disliked it when people who started out with a scathing review that personally attacked the author, would back down when confronted by the author herself, politely defending her choices and asking why the personal comments. They disliked, basically, that an open dialogue allowed people to realize the recipients of their vitriol are human, and not always complete morons.
They did, indeed, become part of mainstream fandom, because the idea of *fandom* vs. just being a fan of the artistic product, includes the concept that behind the pixels on your screen, there's someone typing at a keyboard. Someone who might even want to engage you in intelligent dialogue.
And it looks like that's just too intimidating, or maybe annoying, for them. They would rather have the freedom from responsibilty that posting anonymous "Your fanfic sucks because your mother dressed you funny and your website's ugly" reviews, with no opportunity for rebuttal or discussion, allows. Because it's all about amusing each other, and getting off on the attention, and the other stuff, the actual caring about writing, is just too much work.
I suspect, actually, that they've drowned in their own pretentiousness.