I've never used a screen protector...and only rarely use a case (i hate them, even the small ones). The only screen damage I've ever had was on my 3GS, and it was because i put it in my pocket with a loaded clip from my 40cal. during a qualifying session and it crushed against it one i went down on a knee (the scratch was about the size of your pinkie finger nail in length, and it literally never bothered me unless i looked for it). Other than that obvious brain failure i had, all of my iPhones have been without screen protection and were all perfect when i sold them to the next guy when i upgraded (knock on wood).