The most famous of all the internet laws, formed by Mike Godwin in 1990. As originally stated, it said: "As a Usenet discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches 1." It has now been expanded to include all web discussions.
It is closely related to the logical fallacy “reductio ad Hitlerum”, which says “Hitler (or the Nazis) liked X, so X is bad”, frequently used to denigrate vegetarians and atheists.
Common Godwin's Law appearances include describing women's rights campaigners as “feminazis”, comparing the former US President George W Bush to Hitler, or saying Barack Obama's proposed healthcare reforms are the new Holocaust.