> But if Uber puts heavily regulated cab companies out of business, the alternative disappears.
Then we're into antitrust territory, which is a totally different can of worms.
> Would you be in favor of stores selling water for $100 a bottle before a hurricane?
If this were to happen, it means that there was not enough water in the first place. What's the alternative? Allocate to whoever shows up in line first? Then people who don't want to risk waiting pays someone in the front of the line to buy them a bottle of non-subsidized water, and the price of water hits $100 anyway - it just goes to someone else. As an example of how this works, see ticket sales to high-demand events (Super Bowl, concerts, and the like).
As an example of one strategy that works, one of the most important aspects of US Food policy is that we subsidize production so that food produced far beyond what would otherwise be the market-clearing price. This means that we don't have food shortages in times of disaster. One transportation-equivalent would be building a decent public transit system capable of mass evacuation.