Goodwin's Law
Professor Goodwin, U of I, in 1981 made the observation that Usenet discussions gravitate downhill. He postulated that as the length of a discussion thread grows, the probability approaches one (1) that one participant will introduce the terms "Hitler" or "Nazi". The custom has evolved that the first party to utter "Hitler" or "Nazi" has lost the discussion, and the thread terminates.
Commentary on Goodwin's Law:
Since Godwin's law actually only provides a metric for predicting the mention of nazis in a thread, it is impossible to violate except with an infinitely long thread that doesn't mention nazis.