[brazzy]

> It seems to me that Jeff misunderstood what rule of three means, or he's just trying to re-tell the Wikipedia article in his own words.

Not at all - he's actually making a much deeper point: that something cannot really claim to be reusable until it has actually been used in three different places.

Because if you writer a reusable component for just one product, chances are very high that even if it's technically reusable, it will end up conceptually coupled to that one product too much to actually be useful elsewhere.