Bosses love to praise workers who spend extra hours for the company and ask for no extra pay. They call them "team player" or "model employee", but there are other terms for someone who works long hours for no pay: "workaholic" if it's by choice and "slave" if not. These model employees are either sick or mentally enslaved by the company, neither of which sounds praiseworthy to me.
Mokalus of Borg
PS - Then there are those that are literally enslaved.
PPS - Which is, of course, much worse.