China's Foursquare block tied to Tiananmen Square

Namely, they aren't sure whether this will be a permanent block or temporary. But it appears to be linked to the 21st anniversary of the Tiananmen Square massacre, the 1989 incident in which the Chinese military attacked and arrested thousands of pro-democracy protesters.

Last year, around the 20th anniversary of the Tiananmen Square massacre, China cracked down on sites like Flickr, Twitter, Blogger, and WordPress in an attempt to keep word from spreading about it.