Glass can only be scratched by a diamond or extreme hard metal. I think the scratches you see are actually scratches to oleophobic coating.
Scratches to the oleophobic coating show really well on the black iphone 4
"The only thing that can scratch glass is diamonds" is sort of a fallacy around here. The hardness of glass can vary greatly, so while this may be true for some extremely well crafted types of glass, iPhones are not at this level. This is somewhat concerning since apple specifically bragged about the hardness of the new glass.
I believe that most of the scratches people are getting are from small particles, like grains of sand in their pockets. Sure, many of the hairline scratches are just in the oleophobic coating, this explains why the 3gs and 4 are more prone to scratching, but the scratches do go beyond the oleophobic coating sometimes. I made the mistake of trying to polish out a scratch on my 3gs and removed the coating around the area of the scratch, but you could still see and feel the scratch... I wasn't carrying any diamonds or pieces of metal in my pocket. I would up replacing the glass on my 3gs and I did some tests on the undamaged areas of the old glass to see if I could scratch it. I took some very sharp knives and keys with jagged edges, and I was unable to scratch the surface, an example of how small particles can be more dangerous than things like keys.
On the thread starters original question, no there isn't a way to buff the scratches out of the phone. You'll damage the oleophobic and it will become uneven. Also, depending on how deep the scratches are you may wind up with a rainbow effect.
As far as screen shields go, I have mixed feelings... I'd never use one of those "wet install" skins (zagg, bse, etc) for the screen (I'd use them on the back/sides) as I hate the sticky rubbery texture and the orange peel effect. It takes too much away from the feel and look of the screen. The only screen shield that I've used that I've liked was the power support crystal, its very close to the look and feel of a naked screen... But these are fairly expensive at $20 a pack (includes 2) and they tend to scratch up after a month or two. How much are you really willing to spend on replacing screen shields? Is it worth it to protect the resell value if you spend $80 over a year on screen shields?
For me... I'm a little more protective of my phone because I had to pay the $399 'early upgrade' and I feel like I'll probably skip the next generation of iPhone (meaning I'll have this one one for 2 years), so I went ahead and ordered the power support front/back. But like my 3gs, when the newness wares off, I'll probably stop using them again.
