As in most subjects relating to money management, there’s a wide diversity of opinion on portfolio concentration versus diversification. Few, of course, would argue for the extremes: owning only one or two stocks invites potential disaster (ask those whose entire retirement portfolio consisted of Lucent or Enron stock), while owning hundreds makes it very difficult to outperform the market.

Between the extremes, however, those advocating both more or less portfolio concentration have defensible arguments.