Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why is the fractional-reserve banking not a Ponzi scheme? 
The fundamental underlying difference between a bank and a Ponzi scheme: When a bank lends money and charges interest, people can do things with that borrowed money which are worth it. (Building factories, starting businesses, or just enjoying the comfort and warmth of a single-family home instead of paying rent). This is why fractional-reserve banking is able to work. People may also do things which do not necessarily turn a financial profit (financing large purchases on a credit card) but are worth it in terms of an expenditure. They may also do stupid things (financing useless purchases on a credit card and wasting their money) or otherwise dispose of the money poorly (the new business fails, the home's value plummets, etc). A Ponzi scheme never really bothered to do useful things with the money. Social Security has been mentioned. Part of social security's setup involves the current population of workers paying the current population of retirees; their own retirements will have to be financed by the next generation. This design is not intrinsically a Ponzi scheme: both the population and the economy ought to remain growing for the intermediate future, so there will be at least as much money (and probably much more) for them to pay those bills. Unlike a Ponzi scheme, the idea that it will continue to attract new money to pay out existing claims is a realistic one. The real questions of its sustainability are a matter of specifics: is it collecting enough money to remain functional in the future, or is it outpacing the growth of the economy and the population?