Most of us think we would never fall for a fake rumor. But far too many of us do. This is not new. In 1938, Orson Welles convinced, via a radio drama, thousands of people that Martians were in the process of invading Earth. And the Rwanda genocide of 1994 was fomented by dangerous false claims broadcast on radio. While fake news has always existed, the velocity and therefore the risk today is far greater, making it one of the most dangerous phenomena of modern times. Truth is now so slow to emerge compared to rumor that it can hardly compete.