i.e. "Slaves can be held from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation. " http://en.wikipedia.org/wiki/Slavery
If you have a mortgage you can still refuse to work and just become homeless. Company men will not drag you kicking and screaming to your cubicle and force you back to you home in the evening to watch X-Factor until you vomit and pass out.