> A locker wouldn't have that problem, as there is nothing to break.
There is also no need for collateral or a smart contract in this scenario.
> Public bikes in many big cities don't have that problem either (i.e. there's no assessment of the returned bike).
How does a smart contract improve over the current system?
> A smart car doesn't have to have it either (sensors in the car could detect crashes, for example, and interiors could be built to be tough, like many public cars already - see Paris' AutoLib)
How does a smart contract help?
In all of your examples a smart contract doesn't add anything to the equation because the merchant (or the merchant's automated centralized systems) already have the authority and capability to relinquish deposited funds.
There is also no need for collateral or a smart contract in this scenario.
> Public bikes in many big cities don't have that problem either (i.e. there's no assessment of the returned bike).
How does a smart contract improve over the current system?
> A smart car doesn't have to have it either (sensors in the car could detect crashes, for example, and interiors could be built to be tough, like many public cars already - see Paris' AutoLib)
How does a smart contract help?
In all of your examples a smart contract doesn't add anything to the equation because the merchant (or the merchant's automated centralized systems) already have the authority and capability to relinquish deposited funds.