Sina Weibo is a Chinese version of Twitter. It has became a platform for civilians to speak up and exchange their opinions with social/political elites since 2009. And it has the similar structures and plugins as Twitter in the U.S. So far it has more than 250 million registered users as of October 2011. (http://www.ciccorporate.com/index.php?option=com_content&view=article&id=748:groupm-china-and-cic-identify-luxury-voice-in-chinese-social-media&catid=52:archives-2011&Itemid=158&lang=en)
Besides Sina Weibo, the most popular social media tools in China including Renren (Chinese Facebook), Kaixin, and Tian ya blog.