Sina Weibo China's microblogging market based on active users and 86.6% based on browsing time over competitors such as Tencent Weibo and Baidu's services. The top 100 users had over 485 million followers combined. Furthermore, Sina said that more than 5,000 companies and 2,700 media organizations in China use Sina Weibo. The site is maintained by a growing microblogging department of 200 employees responsible for technology, design, operations, and marketing. Sina executives invited and persuaded many Chinese celebrities to join the platform. The users of Sina Weibo include Asian celebrities, movie stars, singers, famous business and media figures, athletes, scholars, artists, organizations,
Sina Weibo Sina Weibo. Posts on politically sensitive topics are deleted after manual checking. Sina Weibo is believed to employ a distributed, heterogeneous strategy for censorship that has a great amount of defense-in-depth, which ranges from keyword list filtering to individual user monitoring. Nearly 30% of the total deletion events occur within 5–30 minutes, and nearly 90% of the deletions happen within the first 24 hours. On 9 March 2010, the posts by Chinese artist and activist Ai Weiwei at Sina Weibo to appeal for information on 2008 Sichuan earthquake going public were deleted and his account was closed by website's administrator.