As far as I know, this is completely normal, as from personal observation, many if not all cats have this to some degree, including my own cats, and they never seemed to have any problems.
It may actually be a result of wrinkles on the underlying skin. The quality of the hair itself may make the unevenness more pronounced on some cats than others as well. Cats actually have pretty loose skin with a lot of wrinkles. You can observe it easily with the sphynx cat, which is naturally nearly hairless, and so their loose wrinkly skin is quite obvious.
My reason for thinking that it's caused by wrinkles is that one of the most wrinkly areas on the cat is on top of its head and around the face, and many cats I've observed have distinctive furrows in their fur on top of their head. The fur is naturally pretty short there, at least in short haired cats, and so it seems to me to logically follow that the fur will lie a little oddly due to the wrinkles cats have in that area.