The paper by Gary King this reports on sounds like a must read:
What the research showed was a degree of subtlety and sophistication undreamed of in western coverage of Chinese online censorship. In essence, King et al suggested that almost everything we think we know about the Chinese internet is wrong. For one thing, its users do not cower nervously behind the “great firewall”. On the contrary: online debate and discourse in China is as raucous, untamed and virulent as it is here. And yet the government devotes massive resources (200,000-plus people) to watching and censoring the network. So what are they doing? Answer: censoring some predictable stuff (pornography, Falun Gong, Tiananmen, etc); but much of what we would regard as “political” discourse (criticism of local communist party officials, for example) remains apparently unrestricted. There is, however, one type of discourse that isruthlessly and efficiently suppressed: any kind of social media post that could conceivably lead to collective mobilisation – to people on the streets. And this applies even to posts that are favourable to the government!