After the 2010 earthquake in Chile, I remember a guy who got stuck in a room and the phone lines were collapsed. The HSPA network was still alive, and he tweeted where he was and that he needed help. I don't know if he would've died, but it surely helped him.
Here in Chile a guy reported the government about a serious bug on their outsourcing website (chilecompra.cl), they ignored him for months, and he made the bug public (you were able to know your competition's offer to the government just by changing a GET parameter).
He was condemned by a court for breaking the law, more info here (spanish)
What kind of action should one take in those cases? Has this happened before in other countries?