Wow...
These things are supposed to be anodized.
It depends on how
well anodized it is, and how thick the anodized layer is.
Case in point: I have a couple of
mil-spec flashlights that are anodized black. They've been run over by cars, knocked into countless places, smacked hard against rocks and against other pieces of metal, and they still look good as new. The anodization on them is extra thick, and the only exposed aluminum are the parts where the manufacturer etched the model and serial numbers at the factory. And even then, they had to etch so deep that you can feel the sunken-in lettering when you rub your fingers across it.
Then again, these are the type of flashlights that you pay a lot of money for, but you only buy once. If something goes wrong them, even as the result of abuse, they WILL get replaced free of charge.
I was kinda hoping Apple took it to the same level, and got a black one. However... I'm really not seeing the obvious scuffing in those photos. So, I guess only time will tell.