This has been around for awhile and
it keeps coming full circule, I still find it amusing...
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