The mainland's vibrant social media scene has dramatically changed its media landscape but both remain tools of the Communist Party, says the author of a new book, The Party Line . Conventional state media used to take news cues from party mouthpieces such as the People's Daily and Xinhua news agency but now they follow news leads on popular social media, said Doug Young, a former financial journalist who now teaches journalism at Fudan University in Shanghai. People who witness social unrest or accidents can now take pictures with their mobile phones and quickly post them online, putting pressure on state media to come up with an official version of the events as quickly as possible. Twitter is banned on the mainland, but Twitter-like microblog services have hundreds of millions of users. Sina Weibo, the country's biggest microblogging service, has 400 million registered users. But Weibo remains firmly controlled by the party, albeit in a more nuanced way, Young said. "The Communist Party is very much in control … it wants to be able to control the tone of the dialogue, the speed of the dialogue, the subject of the dialogue." Young said the party could also shut down such discussions "any time it likes" if "they are spinning out of control". The Party keeps a close watch on Weibo, and service providers have to self-censor and remove politically sensitive posts when ordered to do so by state censors. Bloggers say that if they write anything about democracy, protests or opposition movements, the keyword system will alert the internet police. Young said social media also helps the government to gauge public opinion. Online discussions about a corrupt Guangzhou official, nicknamed "uncle apartment" for owning 22 properties, went viral on the blogosphere earlier this year, and he was later sacked. Young said Weibo gave a ordinary people a sense of empowerment because it allows them to expose official misconduct. However, discussions of top officials' wealth are blocked on the mainland internet.