Mao Zedong famously said a single spark could start a revolutionary prairie fire. That fear is now driving his Communist Party successors to grapple with how to tame China's expanding legions of microbloggers.

A stream of warnings in state media has exposed how nervous Beijing is about the booming microblogs and their potential to tear at the seams of party censorship and controls.

Chinese microblogs, especially Sina Corp's dominant service, carry plenty of celebrity gossip and harmless fare. But they also offer raucous forums for lambasting officials and reporting unrest or official abuses. It is their potential to stoke popular discontent, even protest, that worries Beijing.

The government feels it's on the back foot about this, said Li Yonggang, a professor at Nanjing University who studies Internet policy, adding researchers and think-tanks had been mobilized to study how to strengthen microblog management.

There's a feeling that additional regulation, formal or informal, is on the way.

The number of Chinese users registered on domestic microblog sites reached 195 million by the end of June, an increase of 209 percent on the number at the end of 2010, according to the China Internet Network Information Center.

Most use Sina's Weibo service, launched in August 2009, or rival Tencent Holding's QQ service.

Officials, however, have not been singing the same tune about how far the government should go to rein in microblogs. Dozens of rival agencies claim a stake in regulating China's Internet and there are certainly different stances, said Li.

Some officials have decried Weibo (pronounced way-baw) as a tool for reckless rumors and subversion; others have defended it as a challenging, but much-needed, window into the public soul.

Despite the jitters, Beijing is extremely unlikely to close microblogs, a step that experts said could unleash its own prairie fire of public anger and distrust that would give even China's thick-skinned leaders pause.

There's this Chinese proverb, 'qi hu, nan xia' (once riding a tiger, it's hard to dismount), and that's the problem the government has -- that it got onto this thing, allowed it to start, and now to shut it down, that would be a nuclear option, said Bill Bishop, a Beijing-based investor and adviser on China's Internet sector who runs the DigiCha.com blog.

It would be surprising if they kill it or completely neuter it, but I think a likely outcome is a set of incremental tweaks and controls, Bishop said of Beijing's approach.

You've got to remember that this is basically a real-time stream of what Chinese people are thinking, and that's not just incredibly valuable to people who care about public opinion, but also for those monitoring security problems, he said.

Stricter controls could include time delays so comments are more finely filtered before spreading online, and demanding at least some classes of users register with their real names, which many do not do now, said several industry analysts.

Beijing also could impose new license conditions on microblog operators, slimming down the number of players to a more manageable and compliant number, some analysts also said.

Microblog regulation will be a game of cat and mouse, said Wang Junxiu, a Beijing-based Internet investor and commentator who follows debates on China's microblogs.

There's clearly a trend toward stricter controls, but the costs of outright shutting them down would be too high.

A MEGAPHONE FOR EVERY CITIZEN

Ever since the Internet arrived in China, the Communist Party has been figuring out ways to monitor and restrict online information and images, and its controls are among the most sophisticated and pervasive in the world. China also blocks popular foreign sites such as Facebook, YouTube and Twitter.

But the explosion of microblog use has pushed China's contest over information into unfamiliar terrain, where censors have lagged like pot-bellied and puffing hunters left flatfooted behind hordes of fleeing rabbits.

Microblogs allow users to issue bursts of opinion -- a maximum of 140 Chinese characters -- that can cascade through chains of followers who instantly receive those messages, challenging censors who have a hard time monitoring the tens of millions of messages sent every day. Inventive users adopt alternative words to get around censorship filters.

We have no other venue for speaking out, because the public's voice can't appear on television or news or newspapers, and so microblogs have become the most effective way for instantly expressing the heartfelt feelings of the public, said Liu Zicheng, a 20-year-old student trawling through his microblog on a web-connected cell phone in a Beijing cafe.

If my microblog was shut down, it would be like I'd lost a habitual part of life, like putting on socks every day before you step out the door, said Liu.

Beijing's worries go beyond the embarrassing exposes of officials' misdeeds and mistresses now common on microblogs. It worries that the torrents of messages could overwhelm censorship and trigger unrest -- a fear reinforced by the role of social media in Arab anti-government uprisings and riots in London.

Weibo can be like a megaphone in the hands of every user, said Li, the Nanjing University professor.

If you shout fast enough and loud enough you can attract widespread attention and there can be a snowball effect so everyone joins in and feels bolder about speaking out.

China felt that force in July when microblogs became a forum for lashing the government over a deadly high-speed rail crash. Images of a peaceful protest against a north China chemical plant in August also spread on microblogs.

Earlier this year, searches and message forwarding on Sina's Weibo site were briefly suspended during government alarm over online calls for protests inspired by the Arab uprisings.

At present, microblogging is still tolerable to the government, but there is a fear of a potential crisis such as the London riots, said Wang Wen, a newspaper commentator in Beijing who has advocated tighter management of microblogs.

If there's a collective incident related to microblogs, the government will step up management of it.

NO SHUT DOWN

But China's leaders would consider shutting microblogs only in extreme circumstances, such as nationwide protests or panic, said Yu Guoming, a professor of journalism at Renmin University in Beijing and co-author of a recent study of microblogging.

Instead, Beijing is exploring ways to tame the microblog so it remains a useful forum for monitoring opinion, but stays within the ultimate grip of authorities. The government is still at the stage of collecting ideas about how to better manage microblogs, said Yu.

Ways of putting microblogs on a tighter leash that have been floated include a time-delay so operators can monitor messages more thoroughly before they go out, and demanding that users who forward messages use their real names, which could deter many of them from challenging censorship.

Even relatively limited steps could draw an outcry from microblog users, said Mark Natkin, managing director of Marbridge Consulting, a Beijing-based company that advises investors about China's Internet and telecommunications sectors.

Tighter controls could also come tied to new license demands, which could be used to reduce the number of Chinese microblog operators and keep only those seen as reliable enforcers of government demands. For now, Chinese microblog sites are formally operating on a trial basis.

Sina has a reputation as a trusted partner of regulators, and might even welcome tougher licensing conditions that deter upstarts, said Li, the professor.

Sina might be happy to guide its microblog space more in the direction of entertainment so the government has fewer jitters, he said.

(Additional reporting by Maxim Duncan in Beijing and Melanie Lee in Shanghai, editing by Brian Rhoads and Raju Gopalakrishnan)

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