I do know where it comes from.
Yet I can't help bringing it up when people bitch about how much work they have to do, mostly because they're burdened by work of their own free will and not because they're being horribly oppressed (as in the case of the phrase of the death camps which echo an older materialistic philosophy).
The materialistic tradition is hard to separate from some pretty terrible things sometimes, though. Hegel's theories about labour, recognition, and conciousness (to grossly oversimplify, because the man loved to write at length) suggested that manual labour (craftsmanship, things done by hand, not the operation of machines which separates man from labour) was the purest and most freeing activity of man because it forces others to recognize him and provide him esteem for his labours and in the objects of his labour sets him aside from appropriation into a dull, alienated mass. It's not hard to see where someone could manipulate this into 'slavery = freedom'.
People tend to shut up when they're forced to perspective and actually realize that they're being melodramatic wankers complaining about a life that is pretty damn good to them. This, I feel, is especially true at university, where even in the face of burdensome debts, people are still persuing an education for the sake of the education itself. Who has that kind of luxury? Not very many people. And they want to bitch at me about how they're slaves to their schedules? Noone's making them do anything in their lives, they have nearly limitless choice, and they complain about how tough their poor little life is. Obviously, I tend to avoid using the phrase flippantly because of its Third Reich implications, but when I hear incredibly privileged people complain I sometimes can't help myself. That people in our society can fancy themselves as slaves to anything boggles my mind completely.
I love the phrase for how uncomfortable it makes people, and for the utility it can hold in terms of making those uncomfortable people self-concious (and, hopefully, through this self-conciousness, change them).
I definitely don't love the phrase for the attrocities that have been committed within its figurative walls, however.