I spent a good chunk of the 1990s writing mutual fund advertising, so much of it that the required caveats and footnotes still trip off the fingers: "Past performance is no guarantee of future results." "The Fund is offered only by prospectus. Please read the prospectus carefully before investing or sending money." Financial services advertising, you see, is ringed about by careful regulation. You can't cherry pick and show off only one good year. You can't make false comparisons. And so forth. One home truth came through that long experience, and I share it here with doubters and fear-mongers who...