That is, it looks remarkably like a private, for-profit lottery. The operation of which, and even knowing assistance or promotion of which, is a third-degree felony under Florida state law. [0]
[0] http://www.leg.state.fl.us/Statutes/index.cfm?App_mode=Displ...
Even if it is random cryptocurrencies, though, if they're smart, the amounts of each of said currencies should add up—at moment of sale, when converted to USD—to a constant amount. In that case, it'd be random ratios of each currency, to fill in a crypto "instrument." (Actually, I would expect this to be true if they have any business sense at all, since the only way to be able to do their books is if they can track their costs, which is only feasible if they have a fixed per-unit cost.)
Or, to put that another way, rather than a lottery per se, this might be more of a crypto-backed Collateralized Debt Obligation issuance where people don't get to know which tranch they're buying. (Which is legal, AFAIK; if it wasn't, the 2007 mortgage bubble couldn't have happened.)
How about if I sell you scrap gold jewelry on eBay? It's value will change before you get it and neither of us really knows how much gold is in it when the transaction takes place.
I don't think that the etfs disclose which assets are held on any given day. From the consumers perspective they are buying some mix of currencies, although they don't know exactly which ones. It seems pretty random to me, just not different from the other note holders.
http://www.orlandosentinel.com/opinion/os-ed-kiss-off-privat...