The iPhone is rated well enough for toughness, but that doesn’t explain the high incidence of broken glass screens. One thing about touch screens is that although some are tougher than others, they’re not quite at par with their older counterparts. A good drop at the wrong angle is likely to put a dent on your screen—and as any owner knows, an iPhone without a touch screen is little more than a shiny paperweight. If it’s the outer glass that breaks—that is, you can feel the crack with your fingers—the touch-screen function usually remains, and you can still interact with your phone. This is pretty common in the iPhone 4, because ...