Beyond ownership, an important class of use cases is promises. Without blockchains, it's hard to determine how well a potential trade partner follows through on

Beyond ownership, an important class of use cases is promises. Without blockchains, it's hard to determine how well a potential trade partner follows through on their promises without a third party that maintains a reputation history. With blockchains, people can provide cryptographically signed promises that give their trade partner the ability to publish their satisfaction or lack thereof. You can retrieve a complete reputation history without a middleman, which is a brand new thing. People are using blockchains for too many things, but that's healthy. It's the only way we can find all the things they're useful for.