Let a thousand filters bloom :: WaPo

In the nation category, China wins the web blocking sweepstakes hands down:

Without question, China's Internet filtering regime is "the most sophisticated effort of its kind in the world," in the words of a recent report by Harvard Law School's Berkman Center for Internet and Society. The system involves the censorship of Web logs, search engines, chat rooms and e-mail by "thousands of public and private personnel."

It also involves Microsoft Inc., as Chinese bloggers discovered last month. Since early June, Chinese bloggers who post messages containing a forbidden word -- "Dalai Lama," for example, or "democracy" -- receive a warning: "This message contains a banned expression, please delete." It seems Microsoft has altered the Chinese version of its blog tool, MSN Spaces, at the behest of Chinese government. Bill Gates, so eloquent on the subject of African poverty, is less worried about Chinese free speech.

But he isn't alone: Because Yahoo Inc. is one of several companies that have signed a "public pledge on self-discipline," a Yahoo search in China doesn't turn up all of the (politically sensitive) results.