My sister once worked for a guy who's management strategy was "Employees should be so unhappy that they are close to quitting but just content enough to not quit."

He thought, that way he'd get the most value out of the employees.

Needless to say, his business wasn't going well because all employees were pissed all the time and that's not a good thing when they all have to work with customers. Also, the turnover was really high. But the boss didn't really notice.