The distinction between tu and vous fascinates me, perhaps because we don't have such a feature in English anymore. While it takes a few seconds of conscious thought for a learner like me to decide between the two in French interactions, the French do it intuitively.
One thing I've noticed is that especially in French television, vous seems to be used often in business situations like when interacting with people on the job, and rarely if ever with friends or family, which would seem to imply it's more formal and polite. But interestingly, two people in a fight might switch to using vous where they would otherwise use tu. At least in American fights, you don't tend to increase your politeness toward your opponent :)
It would seem then that perhaps the concept encapsulated by the French tu/vous distinction isn't quite politeness, but rather social distance, using tu to pull someone close and vous to hold someone away. Is there any merit to this theory?