The market has dropped and many seem to have the answers now, in retrospect of course, and we may turn to them and say - So you are a big shot now? But basically what has happened is that they have ignored the advice of the Three Wise Men of Finance. While portfolio theory can get a bit complex, its basic message that in order to reduce risk a portfolio should contain investments that are not correlated to each other. For instance, if you own Dell and HP or Exxon Mobil and Shell, you can clearly see that these stocks will be correlated to what happens in the industry. To dispel more complexity, it is clear that stocks and bonds are not correlated, at least in most market conditions. So a properly diversified portfolio should reduce the exposure to risk.