Granted, you might not like trying to look around very much when you're riding Metro because you could always end up catching the eye of the crazy person who insists talking to you for the rest of the ride, and follows you out of the station.
So how can you prevent yourself from ending up like this guy on Metro? Peripheral vision, for one, so you don't run the risk of catching the eye of crazy people, but also by being circumspect when it comes to using your phone or tablet. If this guy hadn't had his phone in his hand, he wouldn't have had it snatched by the thief.
It also helps to have tracking software enabled on your phone...Metro authorities have said that's helped to recover some of the stolen items.