It won't do any harm, but it and other screen protectors do little good and negate the advantage of the oleophobic coating on the screen that hides fingerprints and smudges. Unlike most other handheld devices the screen is glass, and harder and more scratch resistant than any screen protector. Unless you plan to keep it loose in a pocket with your keys or pocket knife (which is a really stupid thing to do) you don't need a screen protector. And if you plan to do that you need more than a screen protector. Carry it in a pouch either on your belt or put the pouch in your pocket. This provides much better protection than any screen protector.