There's a reason why smartphone sales are surging past personal computer sales: Smartphones are the new personal computer. They've become our most personal possessions. They hold our secrets, help us communicate with friends and family, and pay our bills. Famous people are no different. Take rappers, for example. If they're not pecking away at a verse, they're tweeting, or emailing, or taking photos for Instagram. That's why if you catch one in public, you're bound to see them with a  black or white rectangle in their hand. But what exactly are they doing on their phones? Read on to find out.