My wife's employer is an apartment management company. Their HR director copied all the company policies and procedures manuals, then bailed to start a competing firm. A few months later, the company demanded that all employees sign non-competes as condition of continued employment.
Because she's worked in the company for nearly 15 years, it's unlikely she would find comparable employment in an unrelated field should she decide to leave. We sought the advice of an attorney who offered some great advice. First he said the company would need to undertake legal measures to enforce the non-compete. Theirs did not provide for any penalty against my wife, so even if they were to win in court, there's no consequences, other than her company is out their legal costs.
Secondly, a non-compete cannot be one-sided, or courts will throw them out. People have a right to work that cannot be forfeited or signed away. Her non-compete was overly broad - both in geography and scope. The language disallowed employees to work in any field the company did business in within the state of Nevada or within 100 miles of any site where they operated. Keep in mind they also demanded the maintenance and landscape workers to sign these non-competes. Our attorney counseled us that those provisions alone would likely nullify the entire document in court. It's not reasonable to tell the guy who mows your lawn that he needs to move across the country if he ever wants to work in yard care again.
I suspect Amazon's warehouse workers would fall under the same protections. Nothing about putting product in a cardboard box is proprietary. This is just some idiot middle manager trying to intimidate employees in an effort to reduce turnover.