Only for a really weird technical definition of "trustless". You have to trust that the smart contract does what's intended, in the way you think it does so. So

Only for a really weird technical definition of "trustless". You have to trust that the smart contract does what's intended, in the way you think it does so. So you need to either trust someone who knows the relevant programming language to audit it, or learn enough to audit it yourself. VS legal contracts, where you have to trust a lawyer to audit the contract but at least have the benefit of laws and bar association ethical rules to constrain the lawyer's behavior. Either way, in practice most people will have to trust someone to safely use any smart contract.