It began as a scattering of acid remarks within earshot of a Rolling Stone reporter. But - thanks in large part to Twitter, the Web, and cable news - barely two days after those remarks were disclosed, a media firestorm ended Gen. Stanley A. McChrystal's tenure as commander of U.S. and NATO Coalition Forces in Afghanistan.

Fast, overwhelming, decisive: It's a case study in how tightly connected 21st-century media can whip a story into a full-on tsunami, with startling consequences for individual careers and national policy.

"Rolling Stone broke the story, but it was Twitter that got the story rolling," says Aram Sinnreich, a media professor at Rutgers University in New Brunswick, N.J. "The peer-produced social media are doing to cable-news networks what cable news did to broadcast. We've gone from the one-day news cycle to every hour on the hour to second by second."

Noah Shachtman, a nonresident fellow at the Brookings Institution and a blogger at Wired magazine, says: "The fact so many of us are networked together enabled the information to spread speed-of-light fast. That turned what might have been a slower-burning flame into an instant conflagration."

How fast? The Rolling Stone article that started it all, Michael Hastings' "The Runaway General," in which McChrystal's team disparages Obama administration officials, doesn't hits newsstands until today.

With the story already yesterday.

On Monday, Rolling Stone spokesman Mark Neschis leaked the story to the Associated Press, which ran an article about one aspect of the story - McChrystal's ire at U.S. Ambassador to Afghanistan Karl Eikenberry - that was circulated on the Internet.

Then Twitter took over. Andrea Mitchell, NBC's chief foreign-affairs correspondent, tweeted: "Rolling Stone quotes Gen McChrystal says Amb(ret Gen) Eikenberry 'betrayed' him with leaked memo last yr doubting Karzai story is out fri."

The rest of the story came out, and soon McChrystal was scoring high on Twitter's Trending list, meaning that lots of people all over the world were firing 140-character tweets about it. (As of Wednesday night, McChrystal was No. 10, behind such hot topics as the World Cup, Wimbledon, and the love life of actress Ana Maria Braga.)

By the nightly TV news Monday, McChrystal was a top story. All this time, hundreds of blogs and news sites were dissecting and debating. Late Monday, the influential website Politico carried a Laura Rozen blog that was commented on and relayed by thousands of readers.

Sinnreich says social networks include ordinary folks, with an ordinary number of connections each, "but there will also be reporters, analysts, political operators, and they are taking part in the conversation as well." Such "super-connected" people, he says, can have thousands of connections, each of whom can bounce a story to his or her personal network. (Mitchell has 9,695 followers on Twitter, many times more than most people - but far fewer than, say, the 1,680,644 Facebook friends of Sarah Palin.)

On Tuesday, Politico and Time magazine published the Rolling Stone article in full online. On MSNBC's Morning Joe, hosts Mika Brzezinski and Joe Scarborough read from it while interviewing Rolling Stone editor Eric Bates. Comically enough, the magazine did not post the article on its own website until, its hand forced by the flood, 11 a.m. Tuesday.

(The Nieman Journalism Lab blogged: "Rolling Stone has been widely criticized, and even made fun of outright, for sitting on Michael Hastings' blockbuster profile.")

Norman Solomon, media critic and executive director of the Institute for Public Accuracy, says the availability of the original piece - everywhere, easily - was crucial.

"People didn't have to wait for it to appear in their mailboxes or on the magazine rack," Solomon says. "Attention could multiply fast, and, while responding to other assessments, people could make their own."

On Tuesday, McChrystal apologized from abroad and got his fateful White House invite. He flew home, and the next day visited the president, was fired, and was replaced. (Much faster than the three weeks and change it took President Harry S. Truman to dismiss Gen. Douglas MacArthur over the latter's criticism of the Korean War effort.)

Solomon says the media storm "accelerated the timeline for the White House to make its decision. . . . When there's all this attention and so few gatekeepers, it's tougher to blow off an issue like this."

To be sure, other factors helped amp up the roar, including a contentious off-year election; a political summer in which stories from the oil slick to Greek economics have taken on white-hot significance; and a clock ticking down to July 2011, when U.S. troops may begin to come home from Afghanistan.

As Shachtman says, "These things don't happen unless there's already a preexisting foundation. The story tapped into a lot of latent anxiety and hostility about the war in Afghanistan that hadn't been given an outlet yet."

Sinnreich adds a psychological component. "A lot of us really know next to nothing about what's really going on militarily in Afghanistan," he says, "so when a schism like this opens up, we think, 'There must be more to this.' " A "collective detection mentality" takes over, he says, and thousands of people start piecing together thousands of bits of information to get a bigger picture.

That's why Solomon thinks the aftershocks will not end with McChrystal: "The focus now is on what's going wrong in Afghanistan. In this day's media world, the reality on the ground can't be set aside so easily."

Contact staff writer John Timpane at 215-854-4406, jt@phillynews.com, or twitter.com/jtimpane.