I heartily endorse Kevin Drum's take on the wildly-overblown notion that Twitter is the only medium that has mattered in Iran these past few days.
One thing that really bothers me about these twitters and first-hand accounts posted on blogs is that there's no way to verify them; I've seen several that either seemed suspect or turned out to be false.
And, yes, cable TV coverage was wretched this weekend, but it's gotten a lot better now. I think a big part of the problem wasn't that cable can't or won't cover a story like this, but that it was a summer weekend and lots of MSM people were checked out--and, probably accurately, assumed many of their readers and viewers were as well.
Update: I should make clear that I wouldn't want to rely on the cable nets for a story like this. It's still the big newspapers and magazines, as well as outlets like PBS and NPR, that I look to for the most reliable reporting put into solid context.