Amazon was forced to shut down IMDB boards, because the discussions on the most popular blockbusters had devolved into flamewars, people posting obscenities and threats, etc. Amazon ended up having to pay a lot of money for workers to police the forums. It does suck that cinephiles having reasonable discussions about less-popular movies got caught in the crossfire, but I totally understand why Amazon did it, and in fact many large companies have taken down fora on their websites for the same reason.