Ponzi Scheme

[MarkBarbieri]

Bernard Madoff is rightly being vilified for running a ponzi scheme. The Wikipedia describes a ponzi scheme as "a fraudulent investment operation that involves paying abnormally high returns to investors out of the money paid in by subsequent investors, rather than from the profit from any real business."

How is that different from what Social Security does? Doesn't it just take the money that I'm paying in to the system today and use it to pay my parents? The money that they paid in wasn't invested, it was already paid out.