How I see it, its just the thin edge of a wedge, and it benefits those that can afford it.
In no other profession do you pay for practicing your profession, which is what you are doing in effect when flying those passengers in that 737. You are being used as CHEAP LABOR. You might not feel that way, but the airline isn't a charity - thats exactly what you are doing - being used.
Those that condone this should really think about the situation. It's all fine for some to say "100 hours is OK" but "500hrs is too much" - sounds like desperate justification to me.
And I came up "the old way".