Memo to Rick Perry, Rush Limbaugh, etc. Social Security is not a Ponzi scheme.
I'll admit that it has many of the earmarks of a Ponzi scheme - e.g. it is largely dependent upon new participants to fund the prior participants. However, Charles Ponzi didn't have the benefit of the ability to tax and print money. Our government has both.
Now, they may be paying us in fiat money worth only a fraction of today's dollar, but the ability to tax prevents SS from being a Ponzi scheme.