Mullpal Air Force Col. Ken Backes has written a scholarly paper on the use of Twitter and similar services for exactly this kind of activity. There was no way for demonstrators to set up a central switchboard for sending an receiving messages, but Twitter provided a mechanism for spontaneous communications outside the reach of the government.
We'll see if this hands-off policy by Barack Obama emboldens the Iranian government and the ruling Ayatollahs.
A significant portion of the Iranian population isn't waiting. They're Twittering their pleas for support.