On UseNet, when you start talking about any subject in relation to Nazi Germany, you invoke Godwin's Law and immediately lose the argument. No rational discourse can come after that point, so you might as well just walk away.

In earlier days, rather than things relating to Nazi Germany, the invocation of the name AdolfHitler? was the sign that common sense had left the discussion.

Rather exhaustive Wikipedia article on it here: http://en.wikipedia.org/wiki/Godwin's_Law