As a longtime WoW player, I wouldn't say its community is hostile or unfriendly, just mind-numbingly stupid. As far as the forums go (I have trade chat muted unless I need something specific, which is rare), there are basically three camps:
1) The experienced folks who write sticky guides and contribute to the general theorycraft of the game;
2) The folks (like myself) who know a lot about the game, contribute periodically, but mostly toss around punchlines and mildly offensive statements;
3) The people who refuse to do any kind of independent reading (which ironically generally takes less time to do than it does to post a questions) and assume that the forum exists to wait on them hand and foot, under the impression that games shouldn't require that kind of effort.
Camp 1 keeps to itself for the most part in a kind of super-clique. Camp 2 is everywhere the action is, like a stolen Visa card. Camp 3, in my experience, comprises the majority of the community, creates the dumbest threads, complains the most while being simultaneously the least informed, and has the worst reading comprehension this side of grade school. Naturally, Camp 3 gets eaten alive. The only reason Camps 1 and 2 are considered hostile is because while they still want to help the new kids, their patience for the self-entitled laziness of Camp 3 is basically nonexistent. And why shouldn't it be? Updated information is within a 10 second Google search; is it really that hard to believe that your question has already been asked by someone else in the 11 million people who play?
Non-gamer communities? HolyTaco and CollegeHumor are some of the best arguments in favor of abortion that I've ever seen.