Rob Williams, co-founder of online music equipment store Dolphin Music, was found dead, presumably due to falling off a cliff, after having gone missing on a snowboarding trip in the Swiss Alps. His friend Jason Tavaria, however, was found alive, thanks partly to the GPS signal from his iPhone, which helped the rescue team pinpoint his location.
The two snowboarders were on a holiday with a group of internet entrepreneurs, which asked for help and discussed the events on Twitter as they unfolded. Their friend Michelle Dewberry, winner of the second season of the TV reality show The Apprentice, tweeted (now erased, but still visible in Google cache) "2 of our ski party been missing since 4pm. Conditions terrible. 1 guy found but trapped. 20 man team searching for other." While Twitter may not be the best choice for communication in urgent situations, it's definitely a great tool for raising awareness or getting feedback about an accident such as this one.