Social networking sites have spread like wildfire in China, ever since the first sites appeared there in 2007. There are now some 210 million people using “social exchange sites,” which is exactly half of all Internet users in China, and the Chinese authorities are saying that the development of social networking sites is “irresistible.” As is often the case in China, the weight of numbers is equaled only by the distinctiveness of their Internet uses. It is this distinctiveness, which borders on the singular – very close links between online socialization and navigation networks, predominance of national sites, content “harmonization,” prevalence of strong links, etc. – that we attempt to bring out here, by successively investigating users, sites and the particular role played by China’s one-party State in the country’s social structures. The legacy of Communism once again stands out as a subtle mix between control over practices and the mobilization of individuals and social organizations and a tolerance of the cathartic and corrective virtues of popular emotion aroused by feelings of injustice.