To understand both the power and the limitations of the Internet under a resolutely authoritarian system of government, it helps to fast-forward from 2003 and the Sun Zhigang case to 2009, to a case that would become just as celebrated as that of the dead migrant worker: the story of Deng Yujiao, a twenty-one-year-old hotel waitress from Hubei Province.

The hotel where Deng worked doubled as one of this increasingly freewheeling country’s countless one-stop spas that offer everything from traditional karaoke, hot baths, and haircuts, to massage and a full menu of sexual services.

When a local Communist Party official who was entertaining friends at the spa took a liking to Deng and demanded sex with her, she refused and was assaulted. Rather than give in to the man’s demands, Deng fought back with a pedicure knife and stabbed her assailant, killing the official and injuring one of his friends. She then called the police herself and calmly awaited their arrival.

Word of the incident traveled fast, initially following much the same pattern as the Sun Zhigang killing, with newspapers picking up the story and local propaganda officials banning further coverage, only to see the news spread like wildfire on the Internet.

Many analysts say the matter might have gradually tapered off and disappeared were it not for what has come to be seen as a signal act in the emergence of an important new force in online activism: the investigative blogger.

Raising money online to conduct his own investigation, a blogger who goes by the name “Tu Fu” made his way into the mental institution where Deng Yujiao had been confined. His photographs of Deng strapped to a bed are widely credited with redoubling public outrage over her treatment.

Huge numbers of what are now universally known here as wang min, or netizens, proclaimed their support for the young woman, demanded that murder charges against her be dropped, and in some cases urged a crackdown on the sex industry or greater protection for its many workers.

Almost overnight, Deng Yujiao became a national figure, and a hero to many. A slogan popular among many women proclaimed: “Anyone could become a Deng Yujiao.”

As with the Sun Zhigang case, with the ever-sensitive anniversary of the Tiananmen Square massacre fast approaching, Beijing tried to quash news and discussion of the official’s killing and its aftermath. “Hubei’s case concerning Deng Yujiao has been under judicial investigation in accordance with the law, and news organizations should halt following up the case temporarily and call back journalists working in Hubei immediately,” read an order issued by the central government’s propaganda authorities a little over two weeks after the incident.

Soon afterward, though, the murder charges against the waitress were downgraded, and Deng, though convicted of the lesser charge of excessive force, was freed. Once again, there would be no government acknowledgment of the role of public opinion, but for millions of Chinese people the impact of the outcry on the web was again unmistakable. “Netizens and other grass-roots forces in cases like Deng Yujiao’s are particularly effective in reaching the masses when the government suffers a credibility crisis,” said Tu Fu, whose real name is Wu Gan, in an interview with the South China Morning Post. “The government is supposed to do what the public expects them to do, and we only hope they do better. The problem is that there never used to be a proper channel or platform for communication, and now the Internet can serve that purpose.”

A great deal changed in China between Sun Zhigang and Deng Yujiao. Most notably, the number of regular Internet users had risen to over 300 million from less than 70 million. The use of advanced mobile phones, often capable of surfing the web at high speeds, had also grown in parallel leaps and bounds, becoming nearly universal in the country’s increasingly affluent big cities.

Along with these developments, a new generation of savvy, highly networked Chinese came of age. Very often, they were no longer content to use these new technologies for the simple voicing of opinions. More and more, China’s netizens were coming together to press demands for justice and meaningful change.

Howard W. French is an associate professor at the Columbia University Graduate School of Journalism. From 2003 to 2008, he was the Shanghai bureau chief of The New York Times. At present, he is a fellow of the Open Society Foundation and is researching a book on China and Africa. French's most recent book is "Disappearing Shanghai: Photographs and Poems of an Intimate Way of Life," with Qiu Xiaolong.