A physical revolution, of course, has to be preceded by a mental/psychological revolution, a growing and widespread conviction that the status quo is simply unbearable, that it's worth a degree of chaos and uncertainty -- likely accompanied by some violence -- to get rid of it. Then there has to be a certain amount of organization and coordination, which the regime is trying to prevent by shutting down Internet sites, etc. -- though apparently Twitter (guess I need to get on that too) is beyond the regime's reach just now.
Too many imponderables and unknowns for me, but what is happening now has the feel of a sustained pre-revolutionary period, with the people testing out their strength. Here's a post from the Register's Orange Punch blog suggesting Obama's approach isn't bad, with some updates and links to analysis. They haven't brought the Revolutionary Guards out yet and they're probably hoping they won't have to. But the ability of the protesters to sustain the movement -- though with 17% admitted unemployment and realistically probably higher -- plenty of people have time on their hands -- is genuinely impressive. A lot of pent-up resentment there.