The following op-ed “Reading Twitter in Tehran? Why the real revolution is on the streets — and offline” was co-written by HLS Professor John Palfrey, vice dean of the library and information resources at HLS and co-director of the Berkman Center for Internet & Society; Berkman Research Director Robert Faris; and Bruce Etling, director of the Internet & Democracy Project at Berkman. Their op-ed appeared in the June 21 issue of The Washington Post.

Pray that today at 4pm Toopkhane Sq. will turn into a sea of green, biggest march in 30 years, Mousavi WILL be there #iranelection

This message, posted on Twitter Thursday morning, is one of countless tweets emerging from the Iranian Revolution Version 2009, in which a love affair between elite young Iranians and the latest Web technologies has become the feel-good story to the otherwise frightening standoff in the streets of Tehran.

Yes, this revolution is being tweeted, blogged and Facebooked — and not just in Tehran. Blogger Andrew Sullivan helped kick off the cyber hype with his June 13 post “The Revolution Will be Twittered?” in which he argued that the use of this platform means that “you cannot stop people any longer. You cannot control them any longer.” And after the State Department asked Twitter to delay a scheduled maintenance last week so that this line of communication between Iran and the rest of the world could remain open, the company’s co-founder Biz Stone offered a somewhat self-congratulatory aw-shucks post on his blog: “It’s humbling to think that our two-year old company could be playing such a globally meaningful role that state officials find their way toward highlighting our significance.”

Certainly, a powerful new force is developing here. Citizens who once had little public voice are using cheap Web tools to tell the world about the drama that has unfolded since President Mahmoud Ahmadinejad was declared the winner of Iran’s disputed election. The government succeeded last week in exerting control over Internet use and text-messaging, but Twitter has proven nearly impossible to block. The most common search topic on Twitter for days has been “#iranelection” — the “hashtag” for discussions on Iran — and global media outlets are relying on information and images disseminated via Twitter feeds.

Yet for all their promise, there are sharp limits on what Twitter and other Web tools such as Facebook and blogs can do for citizens in authoritarian societies. The 140 characters allowed in a tweet are not the end of politics as we know it — and at times can even play into the hands of hard-line regimes. No amount of Twittering will force Iran’s leaders to change course, as supreme leader Ayatollah Ali Khamenei made clear Friday with his rebuke of the protesters, reportedly followed by the security forces’ use of tear gas, batons, water cannons and gunfire to break up demonstrations yesterday. In Iran, as elsewhere, if true revolution is coming, it must happen offline.

First, Twitter’s own internal architecture puts limits on political activism. There are so many messages streaming through at any moment that any single entry is unlikely to break through the din, and the limit of 140 characters — part of the service’s charm and the secret of its success — militates against sustained argument and nuance. (Yes, “Give me liberty or give me death” totals just 32 characters, but Patrick Henry’s full speech exceeded 1,200 words.) What’s most exciting is the aggregate effect of all this speech and what it reveals about the zeitgeist of the moment, but it still reflects a worldwide user population that skews wealthy, English-speaking and well-educated. The same is true of the blogosphere and social networks such as Facebook.

Second, governments that are jealous of their power can push back on cyberspace when they feel threatened. The Iranian state runs one of the world’s most formidable online censorship regimes. In the past week alone, officials have blocked access to YouTube, Facebook and the majority of Web sites most often cited by reformist segments of the Persian blogosphere. They supplement this censorship with surveillance and the threat of imprisonment for those who speak out. Even if they fail to block political speech or organizing activities, the possibility of future retaliation can chill the most devoted activists and critics.

Paradoxically, the “freedom to scream” online may actually assist authoritarian regimes by serving as a political release valve of sorts. If dissent is channeled into cyberspace, it can keep protesters off the streets and help state security forces track political activism and new online voices. As Egyptian democracy activist Saad Ibrahim said last week during a discussion at the U.S. Institute of Peace in Washington, this appears to be part of a long tradition for governments in the Middle East, especially in Egypt, where dissent is channeled into universities and allowed to thrive there, as long as it does not escape the university walls.

Third, the blogosphere is not limited to young, liberal, anti-regime activists; state sympathizers are increasingly active in the battle for online supremacy. Our research into the Iranian blogosphere shows that political and religious conservatives are no less prominent than regime critics. While the Iranian blogosphere is indeed a place where women speak out for their rights, young people criticize the morality police, journalists fight censorship, reformists press for change, and dissidents call for revolution, it is also a place where the supreme leader is praised, the Holocaust denied, the Islamic Revolution defended and Hezbollah celebrated. It is also a place where Islamist student groups mobilize and pro-establishment leaders, including President Ahmadinejad, reach out to their constituents within the Iranian public. Our most recent research suggests that the number and popularity of politically conservative and Islamic bloggers has grown over the past year, relative to the number of secular reformists, possibly due to the events leading up to the presidential election.

Online chatter has enormous value when it offers a window into an otherwise closed society, but much of the cyber conversation in Iran has absolutely nothing to do with politics or revolution. Religion is a major topic for bloggers — and not necessarily the politics of religion, but rather its historical, theological and personal aspects. And the most frequently discussed topic on Iranian blogs? Poetry.

Authoritarian regimes are also eager to employ the Web for their own brand of political activism. In Iran, for example, the Basij, a volunteer paramilitary force under the authority of the Revolutionary Guard, pledged to create 10,000 blogs to combat what it described as foreign elements that are trying to foment revolution online. (The effort ultimately failed.) Government supporters have also carried out increasingly sophisticated attacks against popular Persian Web sites deemed not sufficiently supportive of the government or critical of Israel’s actions in Gaza last winter.

In Russia, those sympathetic to Russia’s renewed geopolitical assertiveness have launched online attacks against critics of the government. During the Orange Revolution in Ukraine in 2004 and 2005, protesters’ Web sites were hacked and temporarily shut down. The same thing happened to official government and banking Web sites in Estonia in 2007 after the government there decided to move a Cold War-era monument that honored Soviet soldiers. And in the run-up to last year’s conflict between Russia and Georgia, so-called DDOS (distributed denial of service) attacks were carried out against Georgian government Web sites. It is nearly impossible to tell who is responsible for these attacks, but in Estonia, the pro-Kremlin youth movement Nashi claimed responsibility for the attacks.

In China, the government has helped train and finance a group that infiltrates Chinese chat rooms and Web forums to combat anti-party discussions. Dubbed the “50-cent party” for the payments they reportedly receive for each pro-government post, these Internet thought cops seek out popular bulletin boards and try to turn around discussions that might be critical of the Communist Party or government policy.

And yet the Twittering goes on. As states such as Iran crack down on online speech and organizing, clever netizens find ways around the controls. In Iran as well as in China, Burma and parts of the former Soviet Union, there’s an on-again, off-again process of citizens speaking out and states pushing back.

Of course, governments always have the nuclear option when it comes to the Internet: They can shut it down and keep it down. It’s what Burma did when monks took to the streets in 2007. It’s the policy of North Korea and Cuba, where only very few people can access the Internet, usually for very narrow purposes.

But most hard-line governments appear more ambivalent. They fear the political repercussions of widespread Internet use, but they may fear the economic and political consequences of banning it even more.

Consider the repeated blocking and unblocking of Facebook over the past year in Iran. When the site is up, citizens use it as an effective organizing tool for an opposition candidate — in this case, presidential candidate Mir Hossein Mousavi’s 65,000-plus Facebook group. The state then gets nervous about the force of this collective action and blocks access to Facebook. After a while, enough people complain that the ban is lifted, only to be reimposed.

The same thing happens in China, where in each of the past four years, Wikipedia has been blocked and unblocked, and where Twitter and YouTube were shut down recently during the 20th anniversary of the Tiananmen Square crackdown.

So who will prevail? Are authoritarian regimes willing to grant their people the autonomy that comes with unfettered access to the Internet? Or will these regimes bend the network to their will through censorship, surveillance and propaganda?

With so many individuals overcoming government efforts to block online communication, particularly via Twitter, it is notable that the Iranian government has not shut down Internet access completely. Similarly, as we discovered in our recent study of the Arabic blogosphere, the Egyptian government tolerates extensive blogging by the Muslim Brotherhood while outlawing its other activities. The Chinese often ease the harshest of their Internet regulations over time. And the military junta in Burma didn’t keep the Net down for long. Ultimately, almost all such regimes choose to leave the Internet more open than closed, then move to regulate specific activities that they deem worrisome.

After all, it appears that people living under authoritarian regimes such as the one in Iran are as addicted to the Internet as the rest of us are. Even though states push back, they can’t keep the Internet down for long without serious blowback from their citizens. Iranian officials have the power to shutter the Internet just as they once clamped down on reformist newspapers, but they may be more concerned now about any move that pushes those watching — or blogging or tweeting — from the sidelines into the throngs of protesters already in the streets.