I have found (from napping in the passenger seat; don't try this while driving :P) that if your head is touching the window, the vibration of the car (I think that's what it is) can produce the "backwards turning effect".

I have just spent ten minutes watching various fans and things, and with a ceiling fan swiching between super-high-speed and high speed under incandescent light, I see a ghostly "image" of the blades turning slowly, in addition to the blurry circle presented by the blades. It's only for a few second, and then it goes away as the speed increases. I've seen this far more clearly with helicopter rotor blades, but whether it was filmed or not I cannot remember.