A report from USA Today says that many fliers refuse to turn off their electronic gadgets during takeoff and landing while flying. Before takeoff and landing, flight attendants instruct passengers to turn off electronics due to the dangers of leaving them on.
Electronics can potentially cause electromagnetic interference, which has not been cited as the cause for any crash, but USA Today reports that pilots believe that EMI is the reason some cockpit instruments go haywire. The devices emit radio signals that can interfere with cockpit instruments and flight systems.