The longer a discussion continues the higher the probability that someone will use an analogy comparing someone or something to Hitler or the Nazis.That's an interesting idea and it's been borne out over and over again from the old usenet groups all the way through current blogs. So what? Why is it anything more than an interesting (and annoying and sad) observation?
Because rules almost immediately sprang up in reaction to Godwin's Law. Think of Godwin's Law as a physics theory and the subsequent rules as the engineering making the theory into something actually useful. These are the two rules which apply whenever Godwin's Law is proven:
1) The person who invokes the Nazi analogy has lost the argument.There are some necessary exceptions:
2) The argument ends as soon as the Nazi analogy is invoked.
1) If the topic discussed naturally calls for talking about Nazi's - i.e. WWII or maybe a comparison of what Stalin did compared to what Hitler did.There may be some other rules or variants which have appeared elsewhere, but I believe this covers most of the rules developed around Godwin's Law (they are certainly the ones I follow). You will often hear all of this referred to, in a shorthand manner, as Godwin's Law. This almost always leads to someone protesting that the entirety of the law and rules is not Godwin's Law - only the law is. Of course, they are technically correct - and usually they are dodging the point: they have proven Godwin's Law and don't want to be subject to the rules which then come into effect.
2) The purposeful invocation of a Nazi analogy in order to shut down a discussion is to be ignored.
Why did these laws come into existence? Well, the problem which they address is that those making internet arguments tend to become emotional. In particular, those losing internet arguments tend to become very emotional (it's easy to remain emotionally detached when you are winning an argument). The loser will often descend into a rant and starting tossing the most hateful terms he can. Hitler and Nazi comparisons carry quite a bit of emotional punch and that punch usually ends up being thrown.
Admittedly, I don't see this as often as I used to. I think this is at least partially because of the identification of Godwin's Law and the development of the rules around it. However, I think that the decline in the emotional, failing-argument use has highlighted a second reason that the Nazi analogies were used: meanness. As the number of emotional proofs of Godwin's Law have declined, because people don't want to be frozen out by it, the use of Nazi analogies as a means of getting in an ugly dig has become more visible. This is not a new phenomenon, it was always around - it just wasn't as noticeable because there were so many people proving Godwin's Law thru emotional outbursts. And it has a key difference. The person proving Godwin's Law in this manner often isn't interested in trying to prove a point - he just wants to get in a dig and Nazi analogies are an easy way to do this because of the emotional baggage they carry.
One can argue - and some do - that this is not what the rules around Godwin's Law are meant to prevent. It doesn't represent an implicit admission that the person arguing has run out of rational arguments and is reaching for an emotional argument to tip the balance back or to strike back at the person who beat her. It's a first strike and can be done coolly and rationally, without the person invoking Nazis being emotional; all this can happen before the merits of the argument have begun to be explored. However, this argument is wrong. The point of the rules surrounding Godwin's Law is to keep the discussion in as rational a mode as possible. There are very few discussions in which the injection of a Nazi analogy does not cause an emotional reaction. It precludes (or at the very least makes difficult) a rational discussion from the point wherein the analogy is made. Thus, it colors the argument and is to be avoided if the discussion is to remain rational.