In November 2010, the number of Chinese using the internet reached 450 million, representing a 20 percent increase in one year. Access to the various international networks such as YouTube, Twitter, Flicker, and Facebook is forbidden, but they have Chinese equivalents. The government makes use of this fact to maintain control over the web by preventing the development of dissident movements. Accordingly, the Chinese web has been cleared of politically sensitive websites. Nonetheless, Chinese surfers play at cat-and-mouse with the censors, sometimes by recourse to innu- endo, and large numbers of them have invaded the blogosphere and other social networking sites on the new 2.0 web,(1) which have become uncen- sored forums for public expression and opposition.(2)Consequently, it quite often happens that various issues create a stir and force the authorities to react. In this way, problems linked to the rapid urbanisation of China have given rise to the social mobilisation of internet users. (3)The French political scientist Michel Offerle (4) makes a distinction be- tween the three major resources that can be mobilised by social move- ments. The first of these is their number, which enables the mobilisation of considerable manpower. The second is the level of their expertise, which depends on the competence of the members of the group and/or their ability to involve people whose acknowledged competence brings with it the power to persuade others. The third is their reliance on controversy to denounce a particular situation and arouse public awareness. The partici- patory aspect of the 2.0 web affords easy access to these three resources. Web users' organisation into networks enables large scale collection and diffusion of information, plus the capacity to present a well-informed al- ternative viewpoint capable of shaping public opinion and, quite often, forcing the official media to take up the issues raised by protests. For its part, the government has also grasped that there are advantages in draw- ing on the same information to shape its own reaction, sometimes by of- fering its own justifications to avoid rumours being spread, or even, on some occasions, by introducing alterations to its urban policies. In effect, official policies are put under surveillance by these cyber-citizens, who are able to challenge their legitimacy. In light of these developing forms of mobilisation in cyber-space, we can raise questions about the contribution made by these new tools by enquiring into the forms, objectives, and ef- fectiveness of these urban social movements, especially in view of their collaborative aspect.At the end of 2010, two experiences led to the establishment of partici- patory sites that asked internet users to provide information in order to denounce current urban policies. By acting as an intermediary for a large number of contributors, their maps, which are compiled collectively, draw primarily on the controversial nature of a particular situation, but they are also aimed at developing a more broadly informed alternative outlook to oppose that of the authorities. In mainland China (see the bloody map insert), this mobilisation is brought to bear on violations related to prop- erty development, whereas in Hong Kong it focuses on environmental is- sues (see the citizen map insert).The real estate blood mapAt first cyber-citizens chose to provoke controversy by relying on the shock value of a situation. For example, in the spring of 2007, the Chongqing nail house - the only one to escape a housing development project - gained international renown thanks to the Zuo.la (or Zola) blogger.(5)This led to the owner being offered improved compensation. The story also put a spotlight, both in China and far beyond its borders, on the wider issue of the forcible eviction of residents of modest means in order to clear space for new apartment blocks, often for the purpose of real es- tate speculation. …