To me, a fair wage is the wage that someone working full time can afford for one person:
[*] minimal shelter in that area (at least enough to keep the rain out and don't freeze to death in the winter, and no major health violations).
[*] minimal food (at least enough so the worker's productivity doesn't get harmed by the constant hunger pains),
[*] minimal clothing,
[*] minimal transportation to/from work (if the minimal housing is 20+ miles from work, one cannot expect the worker to walk every day),
[*] all this without needing to rely on government/charitable handouts.
I believe all full-time jobs should pay at least enough for those four categories. If someone wants any luxuries, or beyond minimal levels of those categories, that person must find another job or work more than full time. Obviously the costs will vary from location to location, so the fair wage will vary from location to location.
I would tend to agree with glenn1, except that history has shown otherwise. Workers in the past were charged to work, charged more than the work paid, and thus the more they worked the more debt they aquired. Workers became slaves to the employeer and faced one of two choices, (a) work for life for that employer submitting to whatever whims that employer had or (b) debtors prison. In this case, the worker no longer has freedoms to find a better paying job, and the "agreement" between employer and employee should not be legally binding since the employee was under duress.
Hmm, I just noticed I passed 10,000 posts sometime yesterday or today. 10,007 is a nice looking number. Maybe I should take today off of posting.