The ability to select stocks, manage them over time and know when to sell them is incredibly difficult, even for professional fund managers.

Mutual fund managers want your money in their funds. They get paid based on assets under management.

Hedge fund managers charge so much more than mutual fund managers; alpha is even harder to come by. They end up selling a variety of things beyond mere outperformance.

Investors tend to discover 'hot' mutual fund managers just after a successful run and just before the inescapable force of mean reversion is about to kick in.

Many hedge fund managers have become billionaires; perhaps this - plus their reputations as the smartest guys in the room - is why they have captured the investing public's imagination.

To know whether stocks are cheap or pricey, we typically look at price-to-earnings ratio. Valuation is a tougher question than many folks realize.