Those of you with LJ accounts may have noticed the increasing references, this past week, to Charlotte Lennox's (an assumed name) The Ms. Scribe Story: An Unauthorized Fandom Biography. If you've passed on reading this riveting, meticulously researched and extremely well-written account of lies, cruelty and manipulation within Harry Potter fandom because you're not a fan of the series or involved with that particular community, I urge you to give it another look. Lennox's document isn't simply an account of one fandom's descent into madness. It is a vital study of group behavior, and of how the online medium accelerates and exacerbates (but by no means causes) the worst impulses of those groups. If you've ever been a member of an online community, no matter how diffuse and ill-defined, if you've ever given any thought to the ways in which the internet redefines the communal experience, you owe it to yourself to read this document.
This is too obscure a topic for me to track down the exact post, but John Scalzi once put forward the theory that an online community's tendency to explode into acrimony and flame wars stands in direct correlation to the narrowness of that community's topic or area of interest. (It's a theory that, I believe, holds true for physical communities as well.) A narrower field of interest makes it all the more likely that a community will get caught up in minutiae, divide along objectively meaningless lines, and inevitably devolve into a self-perpetuating argument for argument's sake, with the original topic of discussion all but forgotten.
It's the dark reflection, if you will, of the charming group dynamic described in the most recent Doctor Who episode, "Love & Monsters", in which several amiable misfits parlay their shared obsession with the Doctor into an all-purpose social club.