The market was rising so fast I knew it couldn't go on forever. I pulled my meager stash out two weeks before the crash of '87 and made an $8K profit. I never went back.

Savvy economic intuition? Not hardly. It could even be argued that I was just a wee bit premature. But the long-term signs have been there for decades. Balance of payments, budget deficits, foreign energy dependence, national debt, loss of industrial capacity, increasing complexity and impenetrability of market instruments, the incredible rise of great wealth and a huge industry that produces nothing of intrinsic value; it doesn't take a mental giant or detailed knowledge of finance to know that it that it was all a sham.

Besides, if you wait long enough, any system will collapse. Entropy will out.