Hardly a ponzi scheme, quite the opposite, there is a transparent accountability factor along with the inherent security which comes from the high level military cryptography.
It is cheaper to mine bitcoins honestly than to try a hack of the system, interesting paradox hey. Completely contrary to current fraudster government controled central banking.
Bitcoin represents a true social revolution. The decentralized currrency aspects are what make it possible and Bitcoin is simply the foundation of many innovations currently being developed.
This is actually bigger than the internet in terms of future applications.