If you're already landless, Amazon coming in isn't going to help you become landed, outside of a handful of the earliest people to get in before the speculators hit. They'll create high paying jobs, but they'll create equally (or likely more) expensive houses.
Anyone wanting to live in Nashville (just to pick one city from the list) who's capable of working for Amazon is also capable of working for someone in Nashville today. And generally, the economics of being tech talent outside these hotbed markets like SV and Seattle are vastly favorable.
That is to say, you're probably better off buying the cheap house in a smaller market on the salary you can command in that market than you are buying a very expensive house on the salary that the very expensive market offers you. Google would pay me more than my current job, but my cost of living would go up by more than my salary -- massively so.
Against local companies (like for in Seattle), it also creates an issue of competition for employment. In Seattle, every job I'm applying to is also being applied to by ex-Microsoft and ex-Amazon employees. It's a much harder competition to land jobs, but in the smaller markets you could find work much more easily.
And if that happens to an extreme degree where it becomes unsustainable, maybe an HQ3 would be in order?