The current edition of Emergency Management Magazine has some statistics (it is a PDF, so see page 22) on the use of technology and how people are getting and disseminating information during emergencies. This comes from a Red Cross survey of 1,058 people (adults).
You have the mainline technology/media systems that take the three top positions, but then Facebook is number four. In total there are four social media tools in the 13 listed. I expect these numbers to only continue to climb.
There is another graphic that should be a bit worrisome to first responders. the question was asked, "If 911 systems are busy, what number will you try to call?" I noted that while texting is only 4%, that number will grow too. Next Generation 911 systems that are IP based will help with that, but how long before a majority of those have that capability? I know Washington State will be 100% digital in 2011, but they will be the first in the nation.