Cunning.

When I was a kid, barbers used to have photos of dashing gents with various haircuts so that you didn't have to describe your hairstyle, just point to it. This guy is sort of doing the same thing. By placing a sticker on his car that depicts a sex act he wants to engage in, he hopes that women (who would also like to engage in the act) will pull him over, point at the sticker and thus ask for mutual oral pleasure. He HOPES...