Twitter is being used not only to allow the outside world to witness first hand what is going on there when other means of traditional communication are severed, but also to interact with the rest of the world in a way that's unprecedented in any previous civil unrest.
As noted by NYU Professor Clay Shirky on the Huffington Post:
I'm always a little reticent to draw lessons from things still unfolding, but it seems pretty clear that ... this is it. The big one. This is the first revolution that has been catapulted onto a global stage and transformed by social media. I've been thinking a lot about the Chicago demonstrations of 1968 where they chanted 'the whole world is watching.' Really, that wasn't true then. But this time it's true ... and people throughout the world are not only listening but responding. They're engaging with individual participants, they're passing on their messages to their friends, and they're even providing detailed instructions to enable web proxies allowing Internet access that the authorities can't immediately censor. That kind of participation is really extraordinary.
Traditional media operates as source of information not as a means of coordination. It can't do more than make us sympathize. Twitter makes us empathize. It makes us part of it. Even if it's just retweeting, you're aiding the goal that dissidents have always sought: the awareness that the ouside world is paying attention.
Teachers who are Twitter savvy can give their students an incredible look at a major world event in a way that no classroom teacher has ever been able to do before unless they were actually teaching in the middle of it.