IMDB is stupid, the power is in the people's hands
We don't like IMDB's chat forums closing down? No problem, all that will happen is that everyone will just visit some of the many new movie sites advertised here on recent threads and continue their discussions there. I think it would be safe to say these other sites will grow quickly thanks to IMDB closing its forums.
Where there's a will, there's a way, and IMDB's decision won't stop everyone from discussing movies anymore, it will simply cause them to do it somewhere else, and probably pretty quickly.
IMDB is being surprisingly stupid because it needs the people, whereas the people don't need it. But by the time they realise this it will be too late.