Yes, controlling is the key. There is a lot of pro-taiwan, anti CCP stuff by American Chinese like the epoch times and nine commentaries on youtube, which I am sure the CCP don't want getting through.

If you are in Shanghai though, I wonder if this includes youtube. I was reading a blog post by some russian nerdy tech guys into climbing skyscrapers, they mentioned they piggybacked some wifi in a hotel in Shanghai and to their surprise facebook was accessible. Don't know if this applies to Beijing though, unless any wai guo ren in Beijing can confirm/deny otherwise?

http://blog.hootsuite.com/china-unblocks-facebook-and-twitter/