I know cases scratch. The question is.. do they scratch the phone itself?
No, it doesnt. And as others have said if you are that worried, then take it off and clean it once a week.
I dont understand why people are so a*** retentive about the condition of their phone...yeah you like to keep things nice and blah blah blah, but go look at your car which probably has more scratches, dings and dents then your phone will ever have. Are you going to shrink wrap it? I didnt think so. Its just a phone.
My first iPhone 4. The bumper did take 2 little chunks of the plastic out near the sleep button. So I stopped rockin it, next day I dropped my 4 and the glass cracked. I brought it into Apple, gave it to my buddy Spencer who works there and swapped me out. Made sure to never use the bumper again. It was definitely the bumper that did the nicks into the plastic. On my new 4 I have an invisible shield, don't like it. Way too many streaking. This week when I'm free I'll be getting ghost armor full body put on.
Cases do NOT scratch the phone. Plastic and Rubber are not > Glass and Steel.
What scratches the phone is getting junk in between the case and the phone. Things like sand are extremely abrasive and can scratch the phone.
Keep your phone in a clean environment, remove and clean the case regularly and you shouldn't have a problem.