More often than you might think, disruptive innovations travel in pairs — at least until they are separated by the markets, which decide one is useful and the other no so much. Sometimes they’re symbiotic. Both may be useful or even necessary — like hardware and software — but that’s not always the case. Consider the strange pairing of blockchain technology and cryptocurrency. The latter, using the former, tried to insinuate itself into society and the economy as the next big thing in, well, currency.