Certainly, there is a powerful new force developing here. Citizens who previously had little voice in public 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 presidential 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 about Iran -- and international media outlets are relying on information and images disseminated by ordinary citizens via Twitter feeds.
Yet for all its 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 do not represent 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 is going to force Iranian leaders to change course, as Ayatollah Ali Khamenei, the country's supreme leader, made clear during Friday prayers with his stern rebuke of the protesters. In Iran, as elsewhere, true revolution can only happen offline.