I'm totally not suggesting that you do this yourself but if you're so very worried about scratching the iPhone 5 and/or a close follower of scuffgate, or whatever they call it these days, know this: stuff scratches. Especially stuff made from aluminum. The iPhone 5 is no different.
Does it suck to have scratches on something brand new that you just spent a lot of money on? Hell yeah it does. But it's probably not a design flaw—nothing like Antennagate—and the aluminum back doesn't have the fragile beauty of the iPhone 4 and 4S' glass back. Swapping shattered glass for possibly scratched aluminum seems like a net positive.