Do you know how many internet websites are blocked in China?
https://en.wikipedia.org/wiki/Websites_blocked_in_mainland_China.
One would think, the obvious reason the Chinese government has adopted this policy to block some of the most popular websites, is due to reasons of political control. I dare to suggest that there is another, more subtle reason that we all should pay attention to. The reason is, to protect Chinese domestic industry.
Just look at some examples, to see how ridiculous things have gone. And the results are obvious. Facebook is blocked, thus leading to WeChat (and Wechat is ever so popular among Chinese in US). Youtube is blocked, thus leading to youku (http://www.youku.com/). Twitter is blocked, thus leading to weibo (http://weibo.com/login.php?lang=en-us).