Everyone here at the show can agree on two things: Foursquare is the coolest application ever and China's government is always looking for new things to ban their country's residents from. I guess they figured since Google gave up on them, they needed a new target, so this week, China has blocked access to Foursquare, due to too many people checking in at Tiananmen Square. This ban, however, does come during the week of the 21st anniversary of the massacre at that location.
Ever since that day, June 4th, 1989, when over 3,000 protestors and students were killed by the Chinese government for protesting against communism, the Chinese government has forbidden any talk or postings about the occurrence. This does extend to the Internet.
Even Google censored data about the incident back in 2006, but with the increase in users on social networking sites, the efforts to cease talk about the topic has become more futile. Last year the government went so far as to block access to Twitter, Flickr and Hotmail days before the anniversary.
This year, protestors used the Foursquare application to post "tips" stating their views and comments. The Chinese government may have learned about this through the application's ability to post users' check-ins to Facebook and Twitter.
At any rate, China has blocked the app. We can safely guess Foursquare will be unblocked sometime next week. But until then, protestors will have to find another way.