Actually, if you search for "Tiananmen" you do still get filtered results.

Searching "Tianamen" (note the missing "n") is not filtered, though. I wonder if this was a purposeful loophole in Google's filtering, or an engineering mistake.

http://images.google.cn/images?hl=zh-CN&um=1&sa=1... http://images.google.cn/images?hl=zh-CN&um=1&sa=1...