Why Facebook is banned in China?

The Chinese government bans the websites it believes to be harmful. A big list of websites is banned inside china and Facebook is one of them.

After a series of violent riots in Xinjiang that led to the death of 197 people, China banned Facebook.

The Chinese government believes that Facebook and other social networks are used to Co-ordinate protests. This is why other social networks such as Twitter were banned as well. (See Why is Twitter banned in China?)

The Chinese government believes that Facebook is used to spread rumors that could threaten the safety of the people. 

One condition for lifting the ban was getting access to content and users' info. Such access was refused, as users didn't like it and so China didn't lift the ban.

Some people argue that the ban remained because China wanted to give local people the opportunity to create successful websites and so push the economy forward.

According to a Quora thread, the Chinese government blocked many sites with user generated content to have better control on what's being said on the internet inside china. (See Why making friends on the web is dangerous?)