[jakevn]

None of which you have listed can be proven by blockchain as it has proofs for today. All would rely on external sources of truth which entirely live outside the verification of the blockchain. The blockchain in these cases would be an immutable chain of unverified facts.

[WalterSear]

* An anonymized reputation system is the equivalent of a transaction ledger. It needs no external source, as long as the involved actors agree to enter into evaluation of each other.

* Digital assets ownership ultimately only require external sources of truth for storage of whatever digital asset they intend to provide. I concur that this would be impossibly expensive to provide via an existing blockchain implementations, without an external point of truth, but still a technically possible feat.

* An entire company on the blockchain? Sure, it's not reasonable at the moment. It was just an attempt to paint a bigger picture. The fact that it's 'not yet reasonable' is why many people are starting to try. By the time it's 'reasonable', someone will have done it.