A friend wrote that the whole top section of his iPhone is dead. It doesn't register any touch at all. Investigating further, it appears that some iPhone touchscreens have started failing. Symptoms begin with lack of touch response in either the top or bottom strip. The problem is being referred to as dead strip.
IntoMobile.com says that Nomura International analyst Richard Windsor released a note to clients indicating that the iPhone’s “dead strip” display problem could become more widespread.
Apple bought the rights to the screen technology used in the iPhone from a Finnish firm. Finnish firm reported that usage led to the same unresponsive display problems after some time. Apparently, 3 to 6 months of “extensive use” would start to degrade the technology and cause a lose of sensitivity to touch-inputs. This suggests that the relatively new iPhone fleet in the US could start to exhibit similar problems with time.
Forum users at Apple Insider and MacRumors are complaining of a “dead strip” starting to plague some iPhones. The “dead strip” on iPhone's multi-touch display loses sensitivity to all touch-inputs. Explains one forum user,
First the very bottom of the screen went out so I could not hit the space-bar on the keyboard, or change to the number/character screen. Then it got worse a few days later, now I cannot hit any of the main function buttons.