I thought the same thing and bought the socks today at the apple store. They do fit on the iphone, albeit snugly. Only the top of the iphone is left uncovered.
Personally, I find it to be a better solution than a full body sleeve with screen cover. I like touching the iphone, but want to keep is safe from scratches in my bag. I also like the way it makes it look like a regular old ipod so people don't stare.