Nitpicking but ain't collectible card games with proof-of-ownership a use case though? In the Magic The Gathering world (for real physical cards) ensuring that thought-after cards are the real thing is an issue. There are brick and mortars grading companies grading the cards. Then you have to trust the seller you're not getting a swapped-in chinese fake.
But another use case I've seen used: fully decentralized messaging, either "pseudonymous" (say tied to a BTC address: there's been a working demo showing on to do this on BTC's lightning network) or fully anonymous messages, using ZK cryptography.
In this case you don't know who send a message to whom. You don't even know if it's a message or an amount transferred.
And if the cryptographic primitives behind that are broken, we would pretty soon know (price would crash).
To me decentralized messaging, fully anonymous using zero-knowledge cryptography primitives, is quite a use case compared to the "we-need-your-phone-number-but-trust-us-our-protocol-and-app-ain't-backdoored-and-we're-not-collecting-any-data" messaging solutions that are out at the moment.
But I agree it's a world obviously full of scam. Still: a blockchain is basically a computer: a very slow and bloated one. But it's also an incredibly correct and very hard to hack computer.
I think there are valid use cases for a fully decentralized computer running advanced cryptographic primitives like zero-knowledge cryptography. To me fully anonymous decentralized messaging is one (and a badly needed one at that). There are probably others.
They are creating a p2p network for live video broadcasting infrastructure, essentially a competitor to "AWS Elastic Transcoder" or the GCP equivalent. The thought is that through an automated decentralized auction for transcoding capacity, customers will always get a better price than centralized cloud computing providers. It would be interesting to see this concept applied to general compute capacity as well. I think I read about something like that elsewhere.
what do they do? Can you point to some successful use-cases today (other than some kittens) where this might apply?
> These "smart contracts" might still be executable centuries later.
chances are that there is no such thing as the Internet a few centuries later in the same way the Telegraph is pretty much dead today!