Marketwatch's Chuck Jaffe recently conducted an interview with the greatest friend the individual investor has ever had: John Bogle.

Bogle banged the drum for the cause he has made famous: Active investing generally leads to poor returns, and the best thing an investor can do is buy index funds and rely on the long-term returns generated by businesses to create long-term portfolio success.

Jaffe asked Bogle for his reaction to the numerous market gurus who have suggested that the future returns of the market will be lower than in the past. Bogle explained that lower dividend yields and slower earnings growth will lead to an average annual return of around 7%, more than 2% less than the historical yield of the market. What should investors do about that? They just have to save more money, according to Mr. Bogle.

Bogle remains a big supporter of traditional index funds, and isn't too impressed with ETFs or hybrid funds. As he said in a recent column, "Mama, what have they done to my song?"

All of his books are terrific, but an absolute must-read is his tome on corporate governance, The Battle For the Soul of Capitalism.

Leverage, the use of borrowed money for investing, goes in and out of favor. When times are good and people are making money, it's great. It amplifies returns (positive or negative) and, particularly in real estate, can lead to mind-bogglingly high return on investment numbers. But the downside is also huge, as anyone who lost a job in the wake of a failed leveraged buyout of the 1980s found out.

My summary of the positives and negatives of leverage is this: Everything that's good about leverage is also bad about leverage.

Having said that, this paragraph from Saturday's New York Times scares the bejesus out of me: Let's say you are very wealthy and have $25 million to invest in a portfolio of hedge funds. Banks like BNP Paribas, Royal Bank of Canada, or Barclays will leverage your investment, say four to one, allowing you to invest $100 million, using derivatives. Barclays estimates that roughly $60 billion to $80 billion in leverage is being put on by investors in hedge funds or funds of hedge funds. Other market players say it is more than double that.

Then you add that leverage to the leverage that the hedge funds are already using. It's like buying stock on the margin, on the margin. And I don't even know what that means. But that's what it's like. Of course, like all leverage, this will be fine as long as the markets are fine, which is kind of like saying driving 120 miles per hour is fine as long as you don't hit anything.

If markets go south, people undoubtedly are going to look back on this leverage on steroids and say "What were we thinking?"