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I reckon it's all down to good/bad luck. I've no case or screen protector for mine, and I've dropped it (on wooden floors) several times, even had it in my pocket with keys & coins on occasion, and no scratch on the front or cracks on the back.

As for screen protectors, I'd never use one. I'd rather have a scratched screen (& thus, a new iPhone) say, once a year; rather than an ugly screen protector or case 365 days a year.
 
I go pure naked, and don't quite "baby" the phone but go a bit easier on her than a POS phone. Generally I treat the iPhone like a phone though.

That said, so far so good - no scratches.
 
Slightly off topic but I trashed my phone today. Accidentally dropped it on concrete, and scratched the back of the phone up quite good. The screen was fine though. I have to say, as much as I was crushed when it happened, I feel better knowing that it's just a phone and now that it's been damaged I hope to enjoy it more as a phone, and not baby it so much. I kind of feel free, if that makes sense.
 
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