Authorities in Pakistan blocked access to Twitter on Sunday, over mention of a contest held in 2010 asking people to draw images of the Prophet Muhammad, and a corresponding Facebook page attempting to make May 20 "Everybody Draw Muhammad Day."

At first it wasn't clear who instituted the ban, but the Washington Post reported the chairman of the Pakistan Telecommunication Authority, Mohammad Yaseen, said “this is not a simple decision, it is a high-level decision."

The Christian Science Monitor reported the "Minister for Information Technology, Raja Pervez Ashraf, issued a blanket ban on the site inside the country, upping the pressure on Twitter as negotiations continue."

The shutdown occurred around Noon on Sunday. Yaseen told reporters that Facebook had been cooperative in shutting down the offensive page, but they had heard no response from Twitter. A few hours later, the ban was lifted.

Are there any circumstances in which it's appropriate for a government to censor social media sites? Tell us in the comments.