Weirdly, the case of Amazon's disappearing "Buy Now" button does, in fact, have something to do with Harry Potter. But it's more about accounting wizardry than the fun kind. We colonials have mostly* been spared being unbuttoned, but on its British site, Amazon has been dematerializing the impulse buy-friendly buttons right and left when disputing with publishers over the vig for book sales. Amazon has not been cutting off its button nose to spite its......