I understand this seems to be a minority opinion on hacker news. I know I don't have the exact parameters of the scam. But insisting on such degenerates into some weird imitation of constructivist logic that seems to claim: if you can't point out exactly when you are going to be ripped off then you can't prove you are going to be ripped off, and therefore you don't know you are being ripped off.
Or: no, I don't know how to make money shorting Bitcoin. But I also don't know how to make money shorting 419 scams. That doesn't mean these things have positive value. Assuming information always has tradable value (i.e. you can go long or go short) is attempting to apply an idea that may or may not be true for investments to a completely different category (scams).
What I think confuses people is we are in the time interval where Bitcoin is a successful scam. So it superficially appears different than any past failed scam you compare it to. But Bitcoin is almost entirely about paying earlier investors purely with proceeds from later investors. A lot of abstract markets and currencies do appear to be similar to this, but tend to have other mitigating features that I just don't see in Bitcoin. (The mitigating factor for traditional currencies is the large state institutions that would lose reputation in a hyperinflation scenario, hasn't always stopped hyperinflation- but it is at least a weak counter-force; for stocks it is the fiction of company control/ownership/dividends/voting-rights; gold the liquidity of the resale market and demand for jewelry; I am not saying these are good institutions, just that you certainly don't want to be even worse.)
I would say to the pro-Bitcoin crowd: if you don't think Bitcoin is a scam, is there any description of a system that you would consider a scam (with our without the Bitcoin name attached)? I say this in seriousness as I really suspect there is some sort of "by definition informed investors can't be scammed, they can only make good or bad investments" element to some of the debates.