Weibo's revenue challenges are far from micro

Mainland online media group Sina Corp is facing twin challenges to its revenue - from a crackdown by the government on bloggers and competition from Tencent's WeChat.

Sina's flagship product Weibo - China's answer to microblogging service Twitter - contributes a quarter of advertising income, the group's second-quarter report last month shows.

But advertising revenue for the Nasdaq-listed group could be hurt if users spend less time on Weibo because the "stars" whose comments they like to follow are posting fewer sharp comments on the service.

Beijing launched a campaign against internet rumours last month, warning that anyone who posts an online message deemed to be defamatory that was forwarded more than 500 times or viewed more than 5,000 times could be jailed for up to three years.

The warning got the attention of Weibo star commentator, real estate tycoon Pan Shiyi, who appeared on state broadcaster CCTV to talk about "social responsibility" of microbloggers.

Until now, Pan has been one of the most prolific posters, and has 16 million followers. But since the warning from Beijing, many celebrity and star commentators - including Pan - have posted less and toned down their criticisms.