More on the Chinese government's Web crackdown: Sina (NASDAQ:SINA) and Tencent (OTCPK:TCEHY) have been forced to shut down commenting on their microblog services until 8 a.m. Tuesday, and state there will be a "centralized clean-up," following the recent spread of coup rumors. In addition, Xinhua is reporting 16 websites have been shut down and six people detained over the affair.