If there was a good way to verify age without needing my full identity, I'd probably be in favor of something like this. God knows I'd prefer my kids don't have access to porn (although I'm not 100% sure I think they shouldn't be able to access it at all until they're 18, they're currently young enough that a total ban is correct).
A few years back, some blockchain enthusiast was extolling to me the virtues of a blockchain backed identity system where you could provide some kind of verified attestation based on a credential - for example, I could use it to prove I'm 18 to the porn site without also giving forth all the other information on my ID.
One of the more interesting ideas I've heard for blockchain. I don't know enough about the topic to know if a chain is _necessary_ for that use case, but I like the idea of being able to verify information in a minimally invasive way.