I hear from a friend who is a political scientist that the hottest study in his world is a paper by Harvard's Gary King on social media censorship in China. Or, as King puts it, "the largest selective suppression of human communication in the history of the world."
The bottom line seems to be that, going by what they censor, Chinese authorities most fear collective action -- that is, not individual protests or outcries, but the threat of people getting together.
Here is a link to the paper. Here is the summary of it from Professor King's website:
Chinese government censorship of social media constitutes the largest selective suppression of human communication in the history of the world. Although existing systematic research on the subject has revealed a great deal, it is based on passive, observational methods, with well known inferential limitations. We attempt to generate more robust causal and descriptive inferences through participation and experimentation. For causal inferences, we conduct a large scale randomized experimental study by creating accounts on numerous social media sites spread throughout the country, submitting different randomly assigned types of social media texts, and detecting from a network of computers all over the world which types are censored. Then, for descriptive inferences, we supplement the current approach of confidential interviews by setting up our own social media site in China, contracting with Chinese firms to install the same censoring technologies as existing sites, and reverse engineering how it all works. Our results offer unambiguous support for, and clarification of, the emerging view that criticism of the state, its leaders, and their policies are routinely published whereas posts with collective action potential are much more likely to be censored. We are also able to clarify the internal mechanisms of the Chinese censorship apparatus and show that local social media sites have far more flexibility than was previously understood in how (but not what) they censor.