II imagine that the Arab Spring a few years ago, which relied heavily on phones to tweet, Facebook, and text each other, might have had different results if their oppressive leaders could convince the phone companies to "kill" the phones of suspected protestors.
They didn't have to "kill" individual phones. They just shut down an entire cell phone network:
http://www.aljazeera.com/indepth/features/2011/04/20114233530919767.html
They weren't entirely successful in Libya, because one of the two providers was not controlled by the government.
The article has an interesting account of how they remained operational.