[madacol]

Well, money is the biggest use-case of it all. If you don't care about inflation (solved via decentralization), then there's the use-case of verifyably programmable money (ethereum)

Another one that I find fascinating is immutability, things like https://opentimestamps.org/ (uses bitcoin's blockchain), it allows you to proof that X piece of information existed prior to time Y.

I know of 2 different paths of assumptions you need to verify that proof:

1. Somewhat trusting bitcoin block's timestamps and the immutability that proof of work provides to the chain of blocks

2. Having a higher bound estimate of your attacker's ability to generate proof of work, and then sum all the available proof of work (it is sequentially chained in the blockchain from the block's proof, till the latest block produced), and compute how much time the attacker needed to spend to fake that proof of work, and that's your proof of the minimum time that must have passed since X was conceived