Multiple Olympians have gone missing from the Olympic Village in London — including seven members of the Cameroon delegation, three from Sudan and one from Ethiopia. One of the athletes is known to have asked for asylum. But the whereabouts of the rest are a mystery. If they have defected, they will join a long tradition of Olympic athletes who have used the Games as an opportunity to escape from their country of origin. Melissa Block speaks with Olympic historian David Wallechinsky, about the history of Olympic defections.