The British had their knickers in a twist over book banding last fall. Nathan Bransford brought up something similar last month.
I would suggest that we already have a sort of book banding here with the age ranges that are posted on children's books. There's no industry standard, of course, and the difference between "8 to 12" and "10 to 14" seems a little slight. Plus YA is a mystery, since it seems to include 12 to whatever. So I guess you could say we have "age banding," it's just not very good.