This is actually something that I'm hoping that eventually homomorphic encryption would enable. Right now it's kind of a bad idea to buy leased out computation time from arbitrary sources. "Hey, I have all these AWS credits and I want to recoup the value of them, so I'll give you a 10% discount on compute time. Uh oh, it turns out I'm also a competitor for your protein folding endeavor, so I'll be analyzing your inputs to steal your secrets and then returning faulting outputs." I suppose you could just demand admin access to their AWS account and lock them out for the duration of your lease, but that's just as bad idea for them as the opposite is for you.

If we had efficient homomorphic encryption, then we could just sell so many operations. Then someone looking to lease second hand computation could just put a counter in the output to make sure they're actually running the full amount and bingo cryptographically certain results.