With storage, we can encrypt and checksum everything client-side in a cryptographically secure manner, and we can have full faith that even though we are giving our data to someone else, they have no way to view the data or tamper with the data.
If techniques like homomorphic encryption gain substantial speedups, I'm sure that we'll start to see decentralized/trustless computing, but for now you really need to be doing your outsourced computing with someone you can trust and someone who is regulated, because it's possible to act maliciously.