Sina HQ in Beijing's Haidian district. Over a thousand people work at this massive open-space office on the 19th floor of a trendy high-rise, staring at their screens, hammering away at their keyboards. The Internet company runs China's biggest microblogging site, Sina Weibo.

Weibo means microblog - a message with no more than 140 characters that can be published by any registered user.

Users can also post photos and videos to Sina Weibo, nurture friendships and make comments, which basically makes Sina Weibo a Chinese cross between Facebook and Twitter.

Chen Tong sits on a couch in his spacious office, chain-smoking. Sina Weibo's editor-in-chief looks like a bulkier Chinese version of John Lennon. "Microblogging is becoming increasingly important," he says. "Everyone can be a reporter today, a citizen's report as they're called."

250 million users, 80 million posts a day

　

The portal, which was set up in 2009, already has a 70-percent share of the Chinese microblogging market and is growing at a breathtaking speed. It wants to double its number of users to 500 million within two years.

Many film stars and politicians use Sina Weibo to reach their fans, and many Westerners, including US actor Tom Cruise and IMF head Christine Lagarde, have also opened accounts to reach a Chinese audience.

Every day, some 80 million Weibo messages are posted and although most are about entertainment or sport, current affairs are also discussed. In June, millions of Sina Weibo users accused the authorities of a cover-up when 40 people died in a terrible train accident. Once the traditional media had picked up on the accusations, the government found it difficult to keep the heated debate under control.

But usually, debates do not get this far. If users post comments that are too critical of the government, the censor steps in. Chen Tong says Sina employees censor themselves, adding that although the platform is very free there are laws in China that have to be observed.

"We let most of the comments that criticize the government through and you will find a lot of them on the site but if the content is too radical then we take action."　

Sina also takes action against rumors and hides what it thinks might be wrong with a message saying "This information is fake" before asking the user to delete the post. The company is currently developing a system to be able to monitor contents more closely.

Keeping strict control

　

In certain cases, Sina might even take the liberty to block users. Deutsche Welle's Weibo account has been blocked several times in the past and today any messages posted always appear with a few minutes' delay.

The Chinese blogger and Internet expert Michael Anti says that the government sees Sina Weibo as a kind of outlet where people can release their pent-up anger, and enjoy the impression that there is some freedom of expression in China, but he adds it does all it can to ensure it does not lose control over such platforms.

Moreover, the central authorities also use Sina Weibo to its own advantage in its fight against regional and local corruption. Many low-level functionaries have been taken to court over affairs that were revealed on Sina Weibo, says Anti. However, any affairs which concern Beijing are immediately deleted.

Last month, the government said that would be stricter monitoring of social networks and chatrooms in future so censorship and self-censorship are likely to get worse.

Author: Christoph Ricking / act
Editor: Shamil Shams