To expand on your point: My lesson from the dot com boom is that's it's very hard to pick the winners. For every Amazon, there were a thousand pets.com. Invest

To expand on your point: My lesson from the dot com boom is that's it's very hard to pick the winners. For every Amazon, there were a thousand pets.com. Investing in DEC, Sun, Yahoo, and friends would not have paid off. That's a broader lesson too. I have an okay -- far from perfect but decent -- track record knowing which national economies will grow, but investing in index funds for those economies rarely yields good returns. I have a tiny portion of my portfolio in various developing markets, and the GDP can rise tenfold with no investment gains. Many very real revolutions have bubbles. Bubbles are the period when people over-invest.