> By that definition, stocks too are ponzis. No. Stocks have an external source of revenue, namely the profit that the company makes by selling its products and services to customers (not investors); and these profits eventually return to the investors through dividends or cash buybacks. In time, those profits are expected to exceed the amount invested, with a significant profit for all investors -- that is, they are expected to be positive-sum games. The market value of stocks reflects these expectations among investors. While some companies fail to achieve this goal, enough of them succeed to make stocks the favorite option of savvy investors.
> By that definition, real estate too is a ponzi. No. Like stocks, real estate creates value while it is being owned, namely the sheltering service it provides to those who live in it. That value returns to the investor (owner) either by him living in the property, or by renting it to others.
> By that definition, gold too is a ponzi. No, gold clearly fails to satisfy that definition on two counts...