[Trezoid]

China is such a massive place that Chinese players in particular don't need to compete outside china. Two of the largest social networks, QZone and Sina Weibo at >645,000,000 and >500,000,000 users respectively are at the level where they're only smaller than facebook and they're used almost exclusively in one country.

You don't need to compete internationally when you can get that kind of userbase domestically, and the Great Firewall is absolutely and to some extent intentionally a big part of that.