Chinese citizens are no strangers to Internet censorship. The Golden Shield (a.k.a the Great Firewall) keeps mainland residents guessing as to what will be banned on any given day. Youtube seems a perennial favorite, but Twitter and Flickr both enjoyed a spell in purgatory in the days leading up to the 20th anniversary of the Tiananmen "Incident".
More effective, though less often mentioned in the overseas press, is the chilling effect the censorship has on Chinese web content, whereby domestic web hosts are forced to register with the government and proactively censor the content on sites under their control. (Not every grass-roots campaign is silenced, for instance the support for cadre-killing waitress Deng Yujiao, whose online following indicates a rising resentment of the corruption of local party officials.)