Well yeah, it's not exactly a Ponzi scheme per se, but it is a lot like oil and other natural resources, but they're a resource and not a currency. It is quite a lot like a natural occurring Ponzi scheme though. I don't anyone has actually explained this yet, the core point I'm getting at is if the supply is inherently built to continually diminish, then wouldn't the price continually increase, and that in itself is can't sustain a stable currency and the people who invested early will never be at risk because their asset will be guaranteed to continually appreciate in value
The same could be said about land. If I bought several hundred acres of land in rural PA as an investment would you say that I am investing in a naturally occurring Ponzi? After all the supply of land is limited.
This is actually the same logic that people use when they said that housing prices would never fall as a group throughout the united states. As we all very well know housing prices did fall by a lot.
With that being said, this is not what the definition of a ponzi is. A ponzi is when an investment run by some central person pays out early investors large returns with the new investment funds of later investors. This is not at all what happens with bitcoin. The price of bitcoin is determined by supply and demand, there is no one person who determines the return that investors of bitcoin receive.