Bitcoins by their definition, are simply a measure of currency, saying "Bitcoin is a naturally occurring ponzi" is like saying "Dollars are a natural occurring ponzi"
I think of dollars like a pyramid scheme. The average people do all the work and the people at the top reap the big rewards simply because they happen to be at the top. They are always whipping us into a frenzy to go out there and make more, borrow more, and spend more.