They're probably sick of the IMDb boards being overrun by trolls and bigots. Still sucks to see the forums go, though, because there really isn't anywhere else to discuss a lot of movies unless they're popular and/or current.
There is a place called TheMovieDatabase, which has all movies and shows, and you can click on a discussion link available on each page. It's different, but kind of the same. I haven't signed up, but some other folks have suggested it.