Nouriel Roubini is right on here.
Crypto-curriencies are not only just an artificial, unnecessary and truly nonsensical commodity, but the peculiar functions that it can only serve is opposite of what is seemingly and expressly intended and implied in multiple and various ways; basically, if the Parties of any transaction/trade want to settle with a crypto-currency, that's fine, if that makes sense to and is agreed by the parties. If a dispute were to ever arise, hopefully the transaction will be valid somewhere for legal arbitration and settlement; for that to be the case, it has to be relative to something and/or everything, as everything is relative; further, you always have to exchange something for the crypto-currency and it must be exchanged and be relative to something and/or everything for it to be of any use/value; it's just a peculiar, nonsensical, commodity; it's not a store of value and it's not money. Further, in order to be a commodity that makes sense, it would need to be valid, effective and enforceable for the use, trade, valuation and pricing of negotiable instruments and be usable and effective as valid and acceptable collateral for trade, which could be hypothetically and and theoretically possible only through a reliable, trusted crypto-Escrow system that's acceptable to and accepted by all Parties, and that serves all inherently necessary and essential purposes and functions as an instrument of Trade. This is just from a natural, inherent and true economic and trade standpoint.
Otherwise, and in general, there's very many disturbing, unfortunate and inherent implications of and from and attributes of crypto-currencies.