Smart contracts does things like "if you replay old transactions on me I get my money back", or "you receive the corresposing private key to this public key if

Smart contracts does things like "if you replay old transactions on me I get my money back", or "you receive the corresposing private key to this public key if and only if you sign this transaction". Clearly the use case is in bypassing a third parties and avoiding risk. There is no clear value in grey areas there. In valuing technology, it is the best use case you can think of that counts, not the worst. Ethereum is a specific form of smart contracts where the use case compared to other forms is perhaps not as clear cut, but that doesn't stop people from speculating on the possibility.