This argument is so basic yet it keeps being repeated over and over on HN... It boils down to you can't expect a return on bitcoin hence it's shouldn't be worth anything. If that argument was true, then gold is a ponzi that shouldn't be worth anything and the same would apply to art. A slightly more advanced rebuttal would be to say, yes but gold has some industrial use and you pay for art because you can enjoy consu…
Bitcoin merely intends to offer a way out: long-term, if demand stabilizes, it should merely match inflation.
But for the next few years or so, I'd expect it to keep growing, which means a lot of volatility.