In February 2011, Tom Cruise tweeted to his followers on Twitter: “We’re having fun talking to you & our new friends at http://t.sina.com.cn/. It’s the Chinese Twitter, but with a lot more functionality.” The fun he was having with his new, superior Twitter delighted China, since it was evidence that Weibo (which translates from Chinese literally as “microblog”) is the belle of the global microblogging ball. Cruise wrote in his giddy inaugural “weibos”: “It’s exciting to be here with you. We look forward to learning more about Weibo” and “Hello! We have some questions about adding a background and posting etiquette. Is this where we should ask? Thank you!” Thousands of eager fans offered instant advice, including: “I can teach you Chinese if you come to Shanghai,” and “Dear Mr. Cruise, As for posting etiquette, I don’t think you should have to worry about that. As long as you don’t post anything offensive religiously, politically, culturally 🙂 Welcome to Weibo.”To his now 3.2 million Weibo followers, Cruise is known as “Tom Brother.” And Tom Brother is not the only Western star with love to show the East; British actress Emma Watson wrote her first Weibo post on July 8, 2011: “Hi everyone, this is the Real Me ( @ EmWatson )! Very excited about my new Weibo page”; N.B.A. star Kevin Durant “weiboed”: “I love China, cannot wait to go there again”; President Bush’s brother Neil joined in with: “In the past 35 years, I have been to China 80 times and am in awe of China’s development.” And Radiohead, in spite of the band’s history of criticizing the Chinese government, arrived with a shy first post: “testing the weibo . . . ”“It’s like ET,” says Cai Jinqing, a Beijinger with more than 120,000 followers. She imitates a foreigner arriving on Weibo by putting her hands in the air and then landing them in front of her in a gesture of fresh arrival and tremendous confusion. “I’m going to touch down into this world and see what it’s like!” Because the Chinese find Western curiosity and friendliness endearing, they celebrate posts like Cruise’s early ones for what Cai calls “willingness to show vulnerability” or “authenticity.” “Especially if you’re famous,” Cai says, “you have to loosen up your language. You have to show China your real self.”

The Chinese social-networking scene is crowded with microblogging sites for China’s 500 million Internet users. Sina Weibo, launched in August 2009 as an accessory to Sina, one of China’s most established portals, is the fastest growing and most talked about, home to more than 250 million users and growing at a rate of about 10 million a month.

Sina is listed on nasdaq. But since the Chinese government restricts foreign direct investment in certain sectors, Sina uses a variable interest entity (v.i.e.) to filter capital through a Cayman Islands bridge company and a chain of intermediaries. The founders in China sort of own it; the investors in New York sort of own it. Sina is run by Charles Chao, a Chinese-born, American-educated journalist and accountant who joined Sina in 1999 as a V.P. of finance and rose through the ranks to become C.E.O. in 2006. In other words, Sina is a perfect example of 21st-century global capitalism; it’s both public and private, local and international, American and Chinese.

The site’s dominance owes a great deal to its courtship of celebrity users; Sina focused on gathering and “verifying” stars, and fans flocked to the site. (It’s a strategy that Western newcomers to the microblogging/social-networking business, like Google+, have attempted in various ways, and with varying degrees of success). Sina Weibo verifies the authenticity of celebrities’ identities by putting a gilded V next to the profiles of public people who meet the requirements for verification—that is, who can prove they’re who they say they are. The rest of us end up relegated to slightly inferior status, with commoner accounts. This two-tier system of verification may seem ironic in a society (and on a microblog platform) that purports to promote social equality, but it both reflects and begets a powerful desire for “authenticity” on the site and in Chinese culture generally. Verification suggests the possibility of distinguishing – on Weibo and beyond – between true and false, original and mimicked, real and fake.

Sylvia Wang, a 25-year-old former project executive for Hachette Advertising, showed me the Weibo page of a beauty with a yearning look, named “Jessie-who-wants-to-be-a-flight-attendant.” Jessie blogs about fashion and her life and has more than 42,000 fans. But it turns out she’s not real. “I made her up,” Wang said, “For advertising. You can make up followers, too; they’re called zombie fans.” The Chinese government announced recently that real-name registration will be required from all Weibo users by March 16, 2012. (Unregistered users may read but won’t be allowed to post or forward tweets. Names will ostensibly be kept confidential by Sina and other Weibo hosts, but there is speculation that having to register may scare off not only zombies but also real Weibo users.)

Wang recently weiboed: “Not everyone has the ability to distinguish between true and false, but everyone has freedom of speech.” It could be the slogan of Weibo, or of China’s youth. Because most Chinese are mistrustful of officialdom and mainstream media, the desire for access to “real” information is particularly acute. And Weibo has provided a taste of that access. In modern China, and especially on Weibo, ordinary people can have a voice, but the Weibo verification team and government officials retain the power to determine what is widely read, what is deemed “true,” and what gets rooted out.

Hung Huang, an outspoken writer and publisher with 3.9 million followers and the nickname “China’s Oprah,” puts it simply: “Freedom of speech was repressed for so long, Weibo is an outburst. People want to express themselves and before social media, they had no way to do it.”

“I’m in denial that I’m in a totalitarian society,” Huang told me over lunch in Beijing. “I’ll pretend I can function how I want to function and see how far I can get. I get messages from my followers whenever I state the obvious, saying, ‘Huang, be careful! We want you around!’”

Huang once posted the entire text (in 140-character excerpts) of a letter by controversial artist Ai Weiwei, who was detained by police last year and was allegedly tortured and intimidated before being released. As Huang weiboed, she and her millions of fans watched the posts go up and then, within seconds, come down. “It was fun,” she said. “It gave me adrenaline. In China you can be naughty and Big Brother still cares. In most countries, no one cares what you say.”

Because authorities do care in China, Weibo has given birth to a new and rapidly evolving language, of abbreviations, neologisms, and substitute words. As Huang’s Ai Weiwei weibos vanished along with any others containing his name, savvy Weibo’ers were evading censors by bending the language, transforming “Ai Weiwei” into the cheerful slogan “Ai Wei Lai,” or “Love the future.” A close enough homonym that users knew what they meant, the characters were still safe enough to be weiboed and re-weiboed thousands of times: “I love the future,” “To love the future is to love yourself,” “I really don’t dare believe that in this society, even love for the future can disappear.” Filmmaker Alex Jia, who formerly taught Chinese language at Harvard, calls the language on Weibo “a kind of revolution. People can invent words and use them in front of an audience. That’s unprecedented.”

“Until I signed on to Weibo, I never saw the real China,” says Cai Jinqing. “Now I can follow what’s happening with a village head in Jiangsu province. Grassroots incidents are gaining momentum, becoming the talk of the day. People can speak for themselves, and be heard.” A student leader at Beijing University during the Tiananmen Square uprising in 1989, Cai left China that summer, studied at Wellesley, and completed a master’s degree at Princeton before returning to China. “Weibo is a genie in a bottle,” she says. “The power is huge, but if it becomes too powerful, the government will shut it down. The government also has to be careful; if they shut Weibo down it will cause a riot. It’s an unspoken, collective agreement that everyone has to behave.”

Part of that quiet pact is that no one touches the “3Ts and 1F”: Tiananmen, Taiwan, Tibet, and Falun Gong; those terms are scrubbed from the Internet in China. And yet information is making it through, and users exert real measures of control over the site. When Fang Binxing, widely considered to be the father of China’s Great Firewall (GFW), the technology that blocks users from accessing sensitive sites, opened a Weibo account, furious Weibo’ers nicknamed him “Eunuch Fang” and within 30 seconds posted hundreds of messages including: “Before, the GFW deprived people’s right to freely access the Internet, now people will deprive your right to use microblog,” and “f–k you 404 times”—a barbed reference to “404 error” messages, which appear when you search the Chinese Internet for blocked terms. Censors couldn’t keep up, and Fang’s account was shut down in less than an hour.

Not all officials get shouted off the site; more than 20,000 government departments and officials have Weibo accounts, the most active of which are police. This is the great surprise of Weibo, says Dylan Myers, former project manager at Google China. “Government officials are being encouraged to get on. It’s a gigantic threat to the propaganda department. Weibo is a great communication tool, a symbol that you’re closer to the people. It’s grassroots. But it’s stripped the party of the ability to control communication. And that’s revolutionary.” Yet it may also be the best service ever provided to the Chinese government. Want to know what your citizens are saying, doing, thinking? Check their weibo’s.

The site was instrumental in channeling both information and rage over news of the scandal-plagued Chinese bullet train in July—beset first by power outages and delays and then by a fatal accident in Zhejiang province. When a signaling failure led to a head-on collision, throwing cars off a bridge, 40 people were killed and close to 200 injured. SOS messages from inside the trains poured into Weibo, and were forwarded hundreds of thousands of times. Within minutes, Weibo became the channel of choice for survivors and witnesses to report the crash and rescue effort; for hospitals to make requests for blood donations; and for users to create and update lists of the injured and dead. But posts turned quickly into furious demands that the railway ministry take responsibility, that the government answer questions, and that someone be held accountable for both the accident and what, after being followed with rapt attention by millions on Weibo, was widely considered to be an inadequate rescue response. Tens of thousands of posts went up in the days following the crash, so many that the Department of Propaganda issued an edict that official media stop covering the accident. But long after the media stopped covering the crash, the conversation on Weibo raged on.

At the end of our lunch together, Huang—“China’s Oprah”—was trying to start following the Weibo for Sora Aoi, a Japanese porn star with close to 10 million followers. (I had just shown Huang an irresistible picture of Aoi’s lunch, a bright green, tumescent pickle rising from two tomatoes.) But Huang kept getting an error message. Half joking, but with a hint of genuine anxiety, she asked, “Have I done something wrong? Am I kicked off? I’m getting a bad connection message. Maybe they’re making sure I don’t get porn, taking care of me.” She feverishly tried to get on until she realized that she hadn’t signed the restaurant’s wi-fi user agreement. As she connected successfully, she smiled and clutched her iPhone so she could watch her Weibo page as she said, “It was just a connection error. I’m still alive.”