At 3:34 a.m. on Feb. 27, something shook Leo Prieto awake. His apartment in Santiago, Chile, was in total darkness.
Nothing worked except for his cellphone. He sent out a message on Twitter: "What the heck was that?" In no time at all, Twitter crackled with messages from all over Chile with stories of serious injuries and collapsed buildings.
Evidently there had been a massive earthquake, and Prieto began to share messages with other Twitter users via his cellphone. In less than half an hour, CNN in Atlanta recognized Prieto as an unofficial hub of information and sent him a tweet asking for his cellphone number.