> A blockchain ensures that some sequence of agreements was made in a way that everyone can trust. If everyone keeps their secret keys secure and solely in thei

> A blockchain ensures that some sequence of agreements was made in a way that everyone can trust. If everyone keeps their secret keys secure and solely in their possession, then no activity can be forged on the network by any significant likelihood. Anywhere this concept has value, a blockchain has value. That's all there is to it. Note an important caveat -- a centralized third party can also provide such a service. So you have to further subdivide the space into use cases where the blockchain has to compete against such services, and use cases where a public ledger is desirable in and of itself.