CK you sound a little open to this concept - forgive me if I'm wrong ? Catch the wave and you make money but for sure, IMHO, someone down the line will lose out. It's a simple gamble and you need to pick it right . . .
Cryptocurrencies are based on 'Fear Of Missing Out' - so as long as everyone piles in, the price goes up. But when the currency runs out of believers - there's nowt 
Apparently, there are around 1500 cryptocurrencies available now - if you can get some Buyers you have lift off - evangelical selling styles are employed.
Obviously 'Blockchain' technology will have applications.
I watched the John Oliver piece when it aired. He is a very insightful and there is little to argue against what he says.
I am not a believer in Cryptocurrencies per se. I am a believer in the technology and how it may have applications; the idea of a 'distributed ledger' that is more universally-accessible, rather than the closed ledger administered by a central entity (as currently happens, and where that central entity can exercise fundamental control) should, in theory, create a free market. I don't believe anyone looks at the Bank of England, Federal Reserve(s), European Central Bank etc. and believes for a nanosecond that these are proponents of absolutely free markets.
Going back to my June 18th post, my point was that if you have something tangible to underwrite the scheme then there is merit to looking at Cryptocurrencies as a vehicle for trading. The current trade war between the US and China is a case in point: the shock waves have yet to hit the markets with full force. Trump is advised by an arch anti-China 'economist' whilst ignoring the fact that the US's closest ally has proved a chemical weapons attack on its territory, which has killed a citizen. It is almost as if the deflection to trade (and the mind-boggling numbers) serve as a useful distraction.
Could the ASEAN nations create a cryptocurrency as a vehicle purely for trade, therefore avoiding the USD? Perhaps we are moving in that direction.