I feel like this is the equivalent argument of "the internet will never support streaming video" from so many years ago. That is not to say that I agree or disagree with the result, but rather that you are trying to fit a new technology into way too broad a category. In twenty or some odd years, we might have the capability for computers to understand "if you mow my lawn I'll pay you $20." But lets leave that aside for now. The question really is: are there problems for which this technology can work? What immediately comes to mind is automated billing. Bills can easily be automatically paid with something like bitcoin. Now, if we extend that to performance based billing, we have something similar to what the OP was talking about: the contract can verify the performance and conduct the payments accordingly. Other areas where this might apply: loans, paying your share of the rent, or auction sites. In short, it has potential. That is not to say that it will replace written contracts any time soon, but rather that I think that it has the potential to do so sometime in the future.