The broader idea that I find interesting however is how to preserve digital content for > 100 years. It's okay if other people don't care about that - I do, and I think it's an interesting set of problem constraints, and was just wondering if anyone else has thought about it.

It's difficult to suggest an actual use case for blockchain, and I am far from an expert, but I think this could be an interesting innovative options for actually using distributed databases to control assets and make collective decisions in a decentralized fashion.