Only good use of a blockchain system is where the cost of trust is larger than the cost of managing the blockchain it's used for.That's all really.Many cryptocurrencies can't be an alternative to money, or anything that needs to be fast (and decentralized). The scaling issue isn't going to get solved because of the technological limitations.It has it's uses, but it's not economical in every use-case currently being developed. I wouldn't see it getting as big as the internet invention though, more like the invention of a better trust or contract holder/issuer.And I'm saying this as someone who 6x'd my investment in bitcoin, and having followed the field as closely as I could since 2013