It is a good idea. Too bad we can't do it.
Although, I already log every movie I watch in three different places:
IMDB
http://www.imdb.com/user/ur37879223/ratings
Letterboxd (for just the past month or so -- I'm digging the service though!)
http://letterboxd.com/timmaster/films/diary/
...And in a custom web app I built, although I won't share that URL.
I also used to log everything in Flixter, but I've since replaced that with Letterboxd.
Unfortunately, that's so much data entry that I usually don't find time to mention it on HDC. I need to get better about that though.