I have a hairline scratch on the screen of my iPhone 4 and I have no idea how it got there. I've had my iPhone for just over 24 hours and I'd like to think I've treated the little girl pretty well - it goes in my pocket, sure, but solo. I also have been using the bumper for most of the time. However, the bumper has been on and off and at some point I must have set it face down on a table with a bit of grit or something underneath there.
In other words, the phone has a small scratch from what I would definitely call normal use.
It's a tiny, hardly noticable scratch. With the screen on, it's invisible - but it's there and I can feel it. I've preordered the Case-Mate Clear Armor Screen Protector for iPhone 4 and am trying not to let the scratch on my shiny iPhone 4 become a scratch on my mind.
After the break, a slightly photoshopped version (just over-sharpened, really, to better show the hairline scratch.