If you put a safe in a storage locker, the police could gain access to the safe and crack it by serving a search warrant on the storage facility, without ever n

If you put a safe in a storage locker, the police could gain access to the safe and crack it by serving a search warrant on the storage facility, without ever notifying you -- and in fact they could get a companion gag order to prevent the storage facility from telling you or anyone else that they had done so. If the service were willing, the police could even gain access by just asking. In that case, you might have a legal claim against the service, but not against the cops. That's probably the best analogy to data in cloud services.