Ponzi does not mean what you think it means. Merely depending on someone to pay you in the future what they say they will does not make an investment a ponzi.When you say there are $50 trillion in liabilities, one must similarly capitalize future tax revenues to normalize the balance sheet.
This argument misunderstands the nature of a Ponzi Scheme. A Ponzi Scheme is a very precise thing. A Ponzi Scheme is characterized by high promised returns backed by nothing that invariably collapses because of the law of large numbers. Every inability to pay, bankruptcy or default is not a Ponzi Scheme. Low returns backed by liabilities that are growing faster than the economy is not a Ponzi Scheme.
Promised SS payments are unsecured liabilities of the government, no different than most government bonds. Government liabilities are a claim on future economic activity. Ponzi Schemes are not. To say that SS is a Ponzi Scheme is tantamount to saying that every government bond not secured by physical assets is also a Ponzi Scheme. To take it to the logical conclusion, one would also say that every unsecured corporate bond or unsecured consumer credit instrument is also a Ponzi Scheme. Every government default, or every corporate or personal default for that matter, is not the result of a Ponzi Scheme.
Also, unlike Ponzi Schemes, government programs can be changed by legislative fiat. We can change how SS is structured tomorrow if we wanted. In a Ponzi Scheme, if the promised returns are lowered, then the scheme collapses because it won't be able to generate enough funds to pay off the prior claimants. That is not the case in SS. SS will not collapse if future benefits are reduced.
It's a bond? Cool where can I sell my bonds? Telling me that my SS "bond" (snicker) is tied to my children's income (sigh) makes it a ponzi. It is a ponzi because it only works if people let the government steal their income by force. The next time they save SS my children will probably have to pay 25% of their income for it. That's up from 2% when it started. An order of magnitude more than when it started. Not only is this a ponzi, it is a ponzi that has been going on for many decades, by force.
Hate to tell you this sport, but every financial asset you have is by your definition a Ponzi scheme. They all depend on someone to pay you in the future. And that someone will have to pay you out of their income, whether its the federal government, a state or local government, a corporation or other business entity, or an individual. What financial (as opposed to tangible) assets do you have that are NOT contingent on the future economy in this way?
Ponzi, schemes are illegal. The only exception being this federally mandated ponzi scheme that uses forced tax payer slave labor to keep it going.