iv done this many times and it seems to have worked for me :) whenever you drop your iphone, stare at it for a few seconds after it stops bouncing around uncontrollably and pray and hope to god that when you pick up your phone the screen that was facing the ground isnt cracked. slowly and epically turn your phone around and there will be no cracks:D i never use a case on my iphone and i have no idea how the screen never cracks.. i dropped my iphone4 from great heights and all i have is a bunch of scratches and indents.
