As it happens, I gave a speech at Google over the weekend on this exact question. Sometimes a "drooping tail" is due to some removeable ineffeciency in the martket, such as poor findability ot limited distribution, and sometimes it's actually the natural shape of demand in that marketplace. The difference between powerlaws, which are "heavy tailed" distributions and "lognormal" curves, which aren't is a fascinating area of research, and I discuss it in this post.

When it comes to evaluating a tail, which matters more: its length or its shape? The answer, of course, is largely a matter of personal taste. But Douglas Galbi argues, compellingly, that we have been so focused on long tails and short tails that we ha...