In another forum, the reason most cited was asking a lady when she was expecting, when, in fact, she wasn't. With me, I sometimes go into woolgathering daydreaming mode and stare at someone without realizing it. And then I suddenly realize it. The object of my staring looks at me angrily, or like I'm some kinda nut. It happens only in a social setting when everyone is standing around yakking. Embarrassing as hell.