I think this is a more complicated issue. I visited an Apple store yesterday to see the colors in real life, mainly to confirm getting a blue one. I was surprised to see the white marks on the back glass. I found light marks on all three colors, but they seem more visible on the blue ones. These marks certainly come from the magnetic stands they use in the store: they have a soft, white pad and a round metal rim around the outside. I'm not sure all these marks are scratches. I was able to rub away some of the marks on the glass with my finger, but not all of them. They might polish out with a microfiber... maybe.
On some blue ones the phone body had some whitish marks. I don't think they are "scratches" in the surface, but marking on the surface. Maybe color rubbing off of the white pad or even the metal rim? The circular marks that match the shape of the magnetic pad were on all the phones, but I only saw the white marks on the blue phone bodies. The blue phone has a much more flat-looking finish than the orange, and the silver looks like most other silver aluminum Apple devices (maybe a little brighter though).
I'm not denying that there are scratches -- aluminum is softer than titanium or stainless steel. But some of what people are seeing, I don't think it's scratches--it's marking. I don't know if it will come off, so in the end it might not make a difference.
In these photos are two different blue phones and you can see the charging stand I described.
Edit: In case you were wondering what I decided, the result for me was I liked the blue, but I'm less sure that's a good choice.