Seems like banks are a Ponzi scheme in their own right.

They take your money and then only keep a portion of it on hand for you to take back. The rest of it they use for their other business ventures. Similar concept to Ponzi schemes.

Ponzi schemes can run indefinitely as long as a majority of the investors don't ask for their money back at the same time. Same as the banks? But when they do it they get a bail out.