Minus Montana, every state is at-will employment of some sort or another. And, I think Montana may even have it in some form now.

> And companies with strong employee unions do not have this issue of suddenly and without notice firing their staff...

Lots of people don't work at a place with a union, and don't have access to unionized employment due to industry, current geography, etc. Also we're seeing a huge anti-union push by a lot of interests right now, recently notable being Starbucks.