ESWN, always a font of fascinating stuff, offered this argument for web censorship in China:

Inevitably, someone is bound to draw the analogy to the Opium Wars. Once upon a time, the Chinese government declared that it no longer wanted to have the opium produced by the East India Company, even though its addicted citizens craved for it. The British Empire decided that anti-free trade practice was bad for business, and employed its mighty naval gunboats to force China to continue to accept more opium as well as pay heavy compensation (such as giving Hong Kong away) for daring to oppose. Today, the Chinese government declared that it does not want any of the pornography produced in Japan and the United States, even if some of its citizens craved for it. But there are forces that are trying to make sure that it fails, although most of these people do not recognize that their efforts have this perverse effect.