How exactly bitcoin resemble a Ponzi scheme? It kinda sounds like you mean pyramid scheme, rather than Ponzi scheme. (Not that bitcoin is a pyramid scheme either...)
In that Bitcoin presents itself as a viable alternative currency, and encourages adoption by people looking for a safe haven from fiat currency. Eventually, though, it could become clear that certain factors, possibly the production function, preclude it from long term viability. The value drops, holding are wiped out, but not before the earliest adopters have already secured their gains.
It's only a Ponzi scheme if you're lying to investors about how much money you have. If you invest in something and then it fails due to some unforeseen factor, that's just bad luck (or bad planning), not a Ponzi scheme.
