Their main use case is maintaining critical/sensitive state information that you want to protect via rules of interaction between multiple parties (that don't t

Their main use case is maintaining critical/sensitive state information that you want to protect via rules of interaction between multiple parties (that don't trust each other) without the need for a trusted intermediary. The contract is tamper proof and only via correctly and cryptographically signing messages/transactions intended for the smart contract will the state of the smart contract change, but only according to the rules defined in the smart contract. The (non-fintec) example I often hear about often is a voting system. (See: https://github.com/stonecoldpat/anonymousvoting https://github.com/stonecoldpat/anonymousvoting , here zk-snarks algorithm is introduced to ensure privacy) Essentially anything that requires co-ordination between parties that don't trust each other over a piece of data (a balance of money, the tally of a ballot) is a perfect use case for smart contracts. But since there is cost to running it on these secure networks it is important that they remain O(1) or at most O(n) time complexity, which for these kinds of applications is often totally enough. (eg. if (the message is signed by the 'owner') { send the funds } else { throw })