In other words, Eth and Aragon would work great, as soon as someone figures out how to build a strong AI that can arbitrate and enforce contracts?

We already have an inscrutable, unaccountable, super-intelligent system that can do that - the courts, the police...

I'm thinking something like unit tests but for real life objects, eg. the chair has to have four legs, specific length, etc. Then have mechanical turks "run" the tests.