The People's Republic of China (PRC) has the world's largest number of Internet users, estimated at 500 million people. Despite government efforts to limit the flow of online news, Chinese Internet users are able to access unprecedented amounts of information, and political activists have utilized the Web as a vital communications tool. In recent years, Twitter-like microblogging has surged, resulting in dramatic cases of dissident communication and public comment on sensitive political issues. However, the Web has proven to be less of a democratic catalyst in China than many observers had hoped. The PRC government has one of the most rigorous Internet censorship systems, which relies heavily upon cooperation between the government and private Internet companies. Some U.S. policy makers have been especially critical of the compliance of some U.S. Internet communications and technology (ICT) companies with China's censorship and policing activities.