It was just after dawn on Aug. 24 when the city of Harbin, in northeast China, awoke to a thunderous crash.
There was nothing on local radio stations to explain what had happened, nor, initially, on the official Xinhua newswire. Local officials were still deciding how they would explain the partial collapse of the city's new bridge, a $300-million span that had opened with great fanfare just nine months earlier.
But while they dithered, China's real source for breaking news – the social-networking site known as Sina Weibo – was alive with reports from Harbin residents who were on the scene and telling others what they could see, and speculating about why another newly built piece of infrastructure had crumbled.
"The ramp of the Yangmingtan Bridge collapsed, with four trucks dropping into the river. Unclear how many victims [it was later confirmed that three people had died and five were injured]. They were trapped by shoddy construction," wrote one of the first Harbin residents to report, posting under an alias. Others quickly noted that it was the seventh piece of sidewalk or road to collapse in Harbin in just nine days.
In their hundreds, the denizens of Weibo began adding more to the online public record, including photographs and shaky mobile phone videos that showed how a piece of the bridge's on-ramp slid clean off its supports and sent the trucks tumbling onto the road 30 metres below.
By the time Huang Yusheng, secretary-general of the municipal government, made his first statement to Xinhua just before 11 a.m. – he tried to blame overloaded trucks for the disaster – he already had been judged in the court of Weibo.
"It's not because of overloading. You should blame the Earth for its gravity instead," one user snarled back.
"In this country, the completion of an infrastructure project lays the groundwork for the beginning of an anti-corruption project," social critic Li Chengpeng wrote on his Weibo account, which has six million readers. Mr. Li's comment was forwarded more than 66,000 times.
Welcome to Sina Weibo, a giant speakers corner frequented by about 300 million Chinese, making it the largest national public square in history.
It's fast, it's rude and, even though it just turned three years old, it's a 24-hour-a-day nightmare for government officials across China, who for decades have kept tight control on information. Many have never before been questioned, let alone ridiculed, in public.
The public backlash after the Harbin bridge collapse was just the latest example of how people have used Weibo (pronounced "way-bwah") to break news, expose corruption and challenge a power structure that has little experience in dealing with public opinion. For the first time, many Chinese can choose which news they want to read and to believe, and let others know what they think about it.
"There was already a growing credibility crisis [in China]. People just don't believe what the government is telling them. Weibo has drastically exacerbated that," says Bill Bishop, the Beijing-based author of Sinocism China, a daily email roundup of news and Internet trends.
Weibo's defining moment came last July when a pair of high-speed trains collided near the coastal city of Wenzhou, killing 40 people. Users trapped on the trains were the first to report the accident, and to call for blood donations to help the injured.
The subsequent online outrage forced the government – after local officials initially tried to cover up the disaster by literally burying one of the train cars – to launch an investigation that eventually laid blame on faulty equipment and a culture of corruption in the Railway Ministry.
Of course, much of the chatter on Weibo – as on Facebook or Twitter– is devoted to celebrities, gossip and sometimes inane updates about people's day-to-day existences. But it can also be credited with creating the first genuine public debates about previously off-limits topics such as the atrociously polluted air in Chinese cities, the privileges enjoyed by the Communist Party elites, and the country's hated one-child policy.
"If the Internet has developed into something approximating a public space in China, Weibo is the white-hot centre of that," says Kaiser Kuo, a blogger who is also the spokesman for Baidu, China's largest search-engine company. "It dictates the national conversation much of the time."
Weibo (the word means "microblog") was actually born out of the ruling Communist Party's desire to control social media. U.S.-based websites such as Facebook and Twitter were just making headway in China when they were blocked in 2009 by the so-called Great Firewall – the country's sophisticated Internet-filtering system – ahead of the 20th anniversary of the bloody confrontations at Tiananmen Square. Shortly afterward, fanfou.com, an upstart Chinese service modelled on Twitter, was forced to shut after it was used to spread information during deadly riots in the restive province of Xinjiang.
Sina was already one of the giants of China's increasingly unique Internet: It was a Yahoo-like portal that provided news, e-mail and a search engine to tens of millions of users. In August, 2009, barely a month after the violence in Xinjiang, Sina Weibo launched a service consciously modelled on Twitter, right down to the 140-character maximum (although you can say a lot more with 140 Chinese characters than with 140 Latin letters). There was a crucial difference: Sina was willing to co-operate with the government and to censor "sensitive" topics.
Internet experts say Sina and other Chinese Internet companies regularly get instructions from the State Council Information Office about which terms are currently considered taboo.
All Weibo posts are scanned automatically, and any containing the forbidden keywords are either deleted, or – if ambiguity is detected – marked for further scrutiny by a growing army of human censors. Among thousands of other topics, it is currently off-limits to write anything on Weibo that directly refers to the coming leadership transfer in China, which is expected to see current Vice-President Xi Jinping introduced as the head of a new Politburo this fall.
"Weibo was blessed by the government. It has never, therefore, been a threat to the regime, by definition," says Jing Zhao, a Beijing-based blogger and political activist who goes by the screen name Michael Anti. "Weibo can't unite people [against the central government] because of the keyword system."
But because much of the censorship is automated, space remains for clever users to get around the government's defences. For instance, the date of the Tiananmen Square crackdown – June 4, 1989 – has long been blocked on Weibo, leading to prolonged discussions of the importance of "May 35th." But the problem with writing in code is that only those who already understand the code can read it.
Mr. Anti and others say that rather than being threatened by Weibo, the central authorities have turned it into yet another tool of control. Local officials who ignore directives from Beijing – or who discredit it with corruption and mismanagement – can now be punished simply by allowing Weibo criticism to continue without the intervention of the censors (as in the bridge disaster).
When the police chief of the southwestern city of Chongqing fled into a U.S. consulate earlier this year and police vehicles surrounded the building, Weibo users were shocked that the photos and comments they posted about the standoff were not rapidly deleted. The reason soon became clear: Bo Xilai, the previously powerful and popular Communist Party boss of Chongqing, had fallen into disfavour in Beijing and was about to be purged.
So is Weibo a threat to Communist Party rule, or does it fact entrench it? The latter might be true in the short term. Replacing Facebook and Twitter with a medium they can control means that China's rulers are unlikely to face the rapidly spreading unrest that has marked the Arab Spring.
In fact, a 2011 effort to organize a Tunisia-inspired "Jasmine Revolution" on the streets of Beijing quickly fizzled. Few in China were ever aware of the call to mobilize, since it came via websites blocked by the Great Firewall, and all discussion on Sina Weibo was quickly shut down.
Score one for the censors, then. But in the longer term? Despite the filtering, Weibo is changing China. The conversation is often angry, and is increasingly leading people to take action at the local level. That must eventually lead people to question the broader system that allows corruption and injustice to thrive.
"Maybe this is working for the government, in that [China] is a big pressure cooker and this is a release valve," says Mr. Bishop, the Internet expert. "But, clearly, this has gotten much bigger than anybody expected."
The network's hottest moments
Wenzhou train disaster
Arguably Weibo's biggest moment to date. When two high-speed trains collided outside the city of Wenzhou on July 23, 2011, killing 40, Netizens on the trains were the first to report the crash and to call for blood donations. When the Railway Ministry tried to hide what had gone wrong – at one point burying one of the railway cars involved – millions of Weibo messages demanded that the car be dug up and an investigation be launched. A government panel ended up concluding that faulty equipment and corrupt officials shared the blame.
For weeks, Weibo users traded information about the health risks posed by living near a molybdenum copper plant like the one the local government planned to build in the city of Shifang, Sichuan. On July 1, thousands of residents took to the streets, shouting, "Kick out the copper factory!" After two days of intense confrontation – demonstrators smashed police cars, while police responded with truncheons and tear gas – the local government halted construction. The latest in a series of "not-in-my-backyard" protests organized via Weibo.
The photos were gruesome: 23-year-old Feng Jianmei lay exhausted on a hospital bed; beside her was the bloody body of her stillborn baby that doctors had forcibly aborted. Because Ms. Feng already had a six-year-old daughter, she was barred from having another by China's one-child policy. Seven months pregnant, she was abducted by family-planning officials in Shaanxi province and given an injection to induce labour. The photos that were uploaded by enraged relatives sparked outrage online – "seven-months pregnant forced abortion" became the most-searched term on Sina Weibo. "This is just the tip of the iceberg," one user wrote.
For centuries, the city of Jinhua in coastal Zhejiang province held a "dog-meat festival" each October without incident. But last fall, Chinese animal-rights activists took to Sina Weibo with a jarring and simple campaign featuring photographs of dogs being caged, skinned, cooked and eaten. "This is not a festival, this is a massacre! Call on China to pass animal protection laws!" read the accompanying petition. It was quickly forwarded hundreds of thousands of times, and Jinhua officials decided to cancel the festival.
Being the local Communist Party boss in rural China used to mean you could misbehave with impunity. No longer. The party secretary in Lujiang, Anhui province, and the deputy party secretary of a Communist Youth League chapter discovered that Weibo really is everywhere in China after they were identified online as participants in orgy photographs that someone uploaded earlier this month, under the cheeky caption, "Comrades in Charge." The younger comrade took the fall, admitting that he and his wife were two of the six swingers involved, while claiming the others were "strangers," not the top party officials they resemble.
If the response to the Wenzhou train disaster was Weibo at its finest moment, the worst was seen in March when some users began posting that they had seen military activity – and even heard shots fired – near Zhongnanhai, the Communist Party's leadership compound in the centre of Beijing. Coming amid the spectacular political defenestration of one-time party star Bo Xilai, Weibo lit up with rumours of an alleged coup d'état. There was no coup, and the online hysteria led to the introduction of a new system that can see Weibo users punished for perceived misconduct.
With research by Yu Mei in The Globe's Beijing bureau.