From The Observer:
The founder of Wikipedia, the online encyclopaedia written by its users, has defied the Chinese government by refusing to bow to censorship of politically sensitive entries.

Jimmy Wales, one of the 100 most influential people in the world according to Time magazine, challenged other internet companies, including Google, to justify their claim that they could do more good than harm by co-operating with Beijing.

Wikipedia, a hugely popular reference tool in the West, has been banned from China since last October. Whereas Google, Microsoft and Yahoo went into the country accepting some restrictions on their online content, Wales believes it must be all or nothing for Wikipedia.

[...]

[Wales said:]  "One of the points that I'm trying to push is that if there's a small town in China that has a wonderful local tradition, that won't make its way into Wikipedia because the people of China are not allowed to share their knowledge with the world. I think that's an ironic side-effect and something the people in the censorship department need to have a much bigger awareness of: you're not just preventing information about Falun Gong or whatever you're upset about getting into China, you're preventing the Chinese people speaking to the world."
It works both ways.  No information in, no information out.  I wonder which way the Chinese government fears most.