The key difference is that banks aren't ponzi schemes. They use your money to actually do things in the world to make a profit, and give you a cut in the form o

The key difference is that banks aren't ponzi schemes. They use your money to actually do things in the world to make a profit, and give you a cut in the form of interest. A ponzi scheme doesn't make any new money, it only redistributes money among its members. This is the fundamental reason they can never be sustainable, and require the majority of those invested to be relatively new to the scheme.