"If your job can be replaced by a computer program, chances are, it will. In fact, Goldin and Katz suggest that prosperity and equality in the U.S. will need a workforce that has more of the mental agility of a Leibniz or a Kircher in order to adapt to rapid technological change."
I really think this is key to understanding this "underclass." It is like a surfer riding a wave, as long as you're up front everything is ok but once you get behind (and fall off the board) it gets harder and harder to get back on. It sounds a little singularity-ish, but we really are seeing an acceleration in the rate of change of technology and culture (or cultural norms like the acceptance of technological interruption at any point).
So I think the question that comes from this is what responsibility do we as a society have to help those that can't keep up with this change? We were just talking about internet access as a human right the other day, so where does this play in?
Is there some sort of digital welfare that we need to set up? Is the fact that non-agile workers can always fall back on retail jobs good enough?