Sina's microblog still falls behind Twitter, which has about 200 million registered accounts. Twitter, however, has been blocked in China following ethnic riots that occurred in the country back in 2009. That move helped open the way for Sina's microblogging service and others in the country to take off.

Sina's microblog, however, has also become a major target for China's Internet censorship. In the last several weeks, the microblog has for terms such as "Egypt" and "Hillary Clinton".

Experts say the move is an effort by the Chinese government to stamp out discussion related to the anti-government protests that have occurred in the Middle East. A group of anonymous activists have also called on the Chinese people to stage a "" to protest China's government. Searches for the word "Jasmine" have also been blocked.