Just to follow up on Mike's post, it's worth remembering that the last supposed Twitter Revolution--in Moldova, in April--turned out to be not all that. From an interview Ethan Zuckerman did with the public radio show "On The Media":
My take on it at this point is that Twitter probably wasn't all that important in organizing the demonstrations. Where I think they were enormously important is helping people, particularly people in the Moldovan Diaspora, keep up with the events in real time.
One thing to keep in mind is that Moldova has a huge population living abroad - it’s more than 25 percent of the country - and they were really attached to Twitter as a source of information. Roughly a quarter of all of the messages posted on Tuesday, the day of the actual demonstrations, were what we call re-tweets. It’s basically saying, hey, I'm quoting this speaker who said the following. And mostly those re-tweets were reports from people who either were in the square or had news from the square.
What you saw on that Tuesday was really people trying to find ways to sort of spontaneously organize a newsroom. By Wednesday, a lot of what seems to be going on in the Twittering is a sort of self-congratulatory, hey, we just held a revolution over Twitter – isn't this exciting? Twitter will change the world.
Then, by Thursday, Twitter’s now being used by a small group of people discussing the events, discussing who’s gotten arrested, discussing what to do next, and, fascinatingly, it looks like it is being used as a disinformation channel by forces who might have been aligned with the government, essentially trying to scare people away from demonstrating again.
Something to keep in mind.