The poor are, in most cases, not qualified to do very skilled high-paying work. That is part of why they are poor. Are the jobs they can get really requiring non-competes? If I take a job at an Amazon distribution center, am I going to be asked to agree that I won't later go to Wal-Mart? And if I do, will Amazon actually bother to enforce that?

Last time I had a decision to make on a non-compete, I did consult with a lawyer and he basically said there are no guarantees, but generally a non-compete cannot be enforced if it prevents you from earning a living.

Edit: the article implies that places like McDonald's do this. I worked there (albeit years ago), and at that time it was not true. We would have been rightly laughed at if we asked for a non-compete on a minimum-wage job like that. It was hard enough to hire people who were reasonably well-groomed, punctual, and energetic. We would not have added unnecessary barriers like that.