10. To keep the hair out of their eyes
9. They are looking for waldo
8. Their mothers told them not to, so they do it anyway.
7. Bothered by how many good bugs are wasted on the windshield
6. It's their way of getting jiggy wit it.
5. They want to impress other dogs with their rugged, windblown look.
4. Much more effective way to distribute drool
3. If they stuck their other end out the window, nobody would think it was cute.
2. Tired of listening to your "Best Of Abba" CD over and over and over.
1. Trying to figure out where the heck all that wind is coming from
Well, If you want to have a real (maybe) scientific way, then go to AskYahoo!