Ya, had thought of it as well at one point. Still think about how fascinating it is though (I LOVE aerodynamics and am fortuneate enough to work in a place that it's a mian point of research) and went as far as to think "Hmm, wonder if dimpling the exterior of a car would assist in fuel milage??
One fascinating thing I saw a few years ago, I think it was NASA that improved the drag co-efficient in an F-16 jet fighter by drilling thousands of tiny holes (with a laser) in the leading edge of the wings and pumping pressurized air into the leading edges (instead of air molecules rubbing on metal, the air flowed freely over air and reduced the vorticies that occur further back on the wing surface.)
Damn man, aerodynamics are amazing!!!!