You have gorilla glass, dude, it's not going to get damaged that easily. I don't have a screen protector and I'm pretty indiscriminate with where I put my phone. No scratches.
Sent from my DROID BIONIC using Droid Forums
^^this^^
I carry mine in my back pocket, no screen protector, no problems.
Of course I have to remove it when I get in the car, sit down, etc....no big deal...I'm just not a big fan of the belt/holster clips with a 4.8" phone. Wasn't a problem using a belt clip with my smaller feature phones back in the day, but the S3 just doesn't look or feel right hanging off my hip.
(Of course that's just my preference)

tap'n