To be fair I think it's less exploitive than Ubers prices surging during a terror attack..
This is sort of a problem if a society depends on them as a piece of critical infrastructure. If a city owns a bus route and needs to evacuate a population, they can just do it by edict.
No one is considering this edge case and how it should be handled at Uber. A company or community that has pride in what they offer would probably provide rides for free during such an anomaly. This is a drawback on the scalability of technology as we currently implement it.