Revolutionary technology? Are cell phones and the Internet a threat to the power of China's Communist rulers--and other nondemocratic governments?

Thousands of people poured onto the streets of China in April to protest Japan's approval of textbooks that they said gloss over Japanese atrocities in China during World War II. The protesters were bound by nationalist anger but also by a more mundane fact: They are China's cell-phone and computer generation.

For several weeks, as the protests grew larger and more unruly, China banned almost all coverage in the state media, but it hardly mattered: An underground conversation was raging via e-mail, text message, and instant online messaging that inflamed public opinion and served as an organizing tool for protesters.

The underground noise grew so loud that the Chinese government tried to silence it by banning the use of text messages or e-mail to organize protests, part of a broader curb on the anti-Japanese movement. But it also seemed the Communist Party had its own future self-interest in mind.

USING TECHNOLOGY TO ORGANIZE

"They are afraid the Chinese people will think, OK, today we protest Japan," says an Asian diplomat who watched the protests. "But the day after tomorrow, how about we protest against the [Chinese] government?"

Nondemocratic governments elsewhere are also learning that lesson. Cell-phone messaging has been an important communications channel in the democracy movement in Lebanon. Ukraine's Orange Revolution last year used online forums and messaging to help topple a corrupt regime.

Few countries censor communications as tightly as China, which has as many as 50,000 people policing the Internet. Yet China is now also the largest cell-phone market, with nearly 350 million users, and the number of Internet users is roughly 100 million and growing 30 percent a year.

CYBER-MOMENTUM

The result is constant tension in China between a population hungry for freer communication and a government that regards information control as essential to its power. Anti-Japanese protesters in China have been able to spread information and loosely coordinate marches in a country where political organizing is illegal.

The anti-Japan protests may not be a reliable predictor of any future popular movements--the Chinese government at first sent signals that the public interpreted to mean that these particular marches were "politically safe."

But the scale of the protests did seem to surprise the government. There is no doubt that underground chatter created momentum. "Text messages, instant messaging, and Internet bulletin boards have been the main channels for discussing this issue," says Fang Xingdong, chairman of blogchina.com, a Web site for China's growing community of bloggers. "Ten years ago, this would have been unthinkable."

In Shanghai, the local police even sent out a mass text message to cell-phone users the day before that city's raucous protest. "We ask people to express your patriotic passion through the right channel, following the laws and maintaining order," the message said. Some marchers saw the message as a signal to proceed, while others took it as a warning.

HARDER TO CONTROL

In the anti-Japan protests, people also sent old-fashioned chain letters to friends via e-mail or text message. Many in Shanghai learned of the march from the Internet.

Typical is a 23-year-old professional who asked to be identified by her English name, Violet. After receiving an instant message to join the Shanghai protest and recruit others to do the same, she sent instant messages from her computer at work to communicate with 50 people on her "contact list."

Within weeks, however, the government began cracking down on people using these technologies to foment anti-Japanese protests.

But many analysts agree that screening the Internet and cell phones is far more difficult than simply ordering state-controlled newspapers or television stations to censor a subject.

One reason is that a growing number of young Chinese have multiple e-mail accounts, including some with providers based outside China that are not filtered by the government. About 27 percent of China's 1.3 billion people own a cell phone, a rate that is far higher in big cities, particularly among the young. Indeed, for upwardly mobile young urbanites, cell phones and the Internet are the primary means of communication.

"If people can mobilize in cyberspace in such a short time on this subject," says Wenran Jiang, a scholar of China-Japan relations, "what prevents their from being mobilized on another topic, any topic, in the near future?"

Jim Yardley in Beijing

Jim Yardley covers China for The New York Times. He is based in Beijing.