If you want to make money investing, one of the most important rules is to avoid following the herd when the numbers don't support the hype. One sign a "herd" mentality has taken over investors is when people proclaim that old, tested investing models no longer apply and use generalities to describe what's going on in the market instead of relying on hard data. Excessive interest in sometimes risky investments due to insecurity that one might miss out on a hot stock or fund is one of the key ingredients in investment bubbles, according to a July 2006 study by Peter DeMarzo and Ilan Kremer of the Stanford Graduate School of Business, along with Ron Kaniel of Duke University's Fuqua School of Business. If you have ever wondered why people continue to invest even when it becomes obvious that a stock or fund is risky and a bubble is forming, the study finds that it isn't so much that people believe that they are buying into a good investment, but simply that they are afraid that others will make money on the investment and they won't. According to the study, many people fear being left out of the possible rewards from the investment much more than they fear actual risks.