"Nothing says ‘police state' like detaining kids for eating ice cream."

This is the best line in Internet guru Clay Shirky's new book, Here Comes Everybody, and he knows it. He wisely recycles it for an appreciative crowd on Thursday, the day of the book's release, at a talk sponsored by Harvard's Berkman Center for Internet and Society. He's talking about flashmobs in Belarus, which we'll get back to later. But let's begin at the beginning.

Email is the granddaddy of seemingly frivolous Internet applications. "It was an afterthought on the original internet. It was not part of what they sold to ARPA," says Shirky, an adjunct professor at NYU's Interactive Telecommunications Program and an Internet consultant for Nokia, BBC, Lego, and the U.S. Navy. Email was just a simplified file-sharing program. But within 3 months, email was 70 percent of traffic on the fledgling Internet.

It wasn't because email was a fast way to send a message to someone, or even that it was a fast way to send a message to a lot of people—there were already ways to do both those things pretty efficiently. What really made email take off, says Shirky, was the Reply All button.

Of course, everyone professes to hate the Reply All button and periodically swears bloody vengeance on its abusers. But the Reply All button offers us the power to turn a communication into a conversation (and sometimes even a community) with virtually no effort at all. No coordinating meetings or teleconferences, no need for synchronicity (anyone can read their email at any time and still be a part of the group), and no duplication.

"For the first time in human history," says Shirky, "our communications tools support group conversation and group action." Governments, ancient and enormous institutions like the Catholic Church, and massive corporations used to thoroughly dominate the landscape because only they could afford the high costs of coordination of large numbers of people. But now, for the first time, coordination (like talk) is cheap.

Consider the case of Gnarlykitty. She's a college student in Bangkok who mostly blogs about her new cell phone or posts pictures of her friends at clubs. But when Thailand found itself mid-coup in 2006 with major media outlets heavily restricted, she posted a bunch of photos and some of her thoughts on what was happening.

She became a minor celeb, posting to Wikipedia—which was aggregating news about the coup—and blogging summaries of events intermingled with tidbits like this one:

Long lost friend asked on MSN: "Hey Kitty how are ya??" Me: "Great! Country is breaking but great!"

When things calmed down, she wrote: "OK I'm giving it a rest. I live blogged because all the news channels were cut off and all the websites were blocked. Now all major newssites and channels are up and running, my job is done. Besides, school back to normal tomorrow so I need to get back to my work." And that was that. The next day she posted about shoes: a "new pair of Nine West wedges" to be exact.

"She wasn't a full-time journalist," writes Shirky, "she was a citizen with a camera and a weblog, but she had participated in a matter of global significance at exactly the time when the traditional media were being silenced." The government closed down old coordinating institutions like media and activist groups, but was powerless to stop non-institutional actors.

Let's now return to the Belarussian ice cream eaters (Gnarlykitty would want us to).

They were a flashmob, of course. Flashmobs started out as a critique of hipster culture. Bill Wasik, an editor at Harper's, started sending out messages (as "Bill from New York") to large groups, suggesting that they do things like make bird noises on a ledge in Central Park. He intended it as a kind of elaborate thumb in the eye of hipster conformism. Others caught on, perhaps omitting the irony, and did things like staging a silent rave in Victoria Station. The New York Times runs a smug story on how flashmobbers "have nothing better to do" with their time. And, as the cliché goes, once The New York Times has heard of a trend, it must be so over, right?

But then, suddenly, flashmobs found their true calling: On a blog in Belarus, someone proposes a flashmob. The plan is to get together in October Square—the preferred site for political action, and a place where concerted action is banned—and eat ice cream.

Black clad secret police appear and drag dairyphilic kids bodily out of the square. "The problem with a group eating ice cream wasn't the ice cream, it was the group," says Shirky. "Lukashenko, the leader of Belarus, is the last great Eastern European dictator [but] the Lukshenko government can't penetrate the conspiracy, right? The whole thing is being done on the web. And they can't stop the group from entering October Square because they're not a group when they enter October Square."

Photos went up online almost immediately. The thinking was that it's tough to be really consistently oppressive and brutal when the world is watching. (Shirky: "The bug in the system is that the West cares quite a bit less about Eastern European dictatorship than it used to.")