Erik Brynjolfsson and Andrew McAfee, two MIT economists, recently wrote a book about this, called The Second Machine Age (here:
http://www.amzn.to/0393239357). We're teetering on the edge of economic shifts, and we have a lot of questions we're going to need to ask about how people will live in a world where jobs simply aren't available.
When 60% of the workforce is unemployable, either there will be massive unemployment, and the crime, poverty, and starvation associated, or there will be a massive paradigm shift in how we think about employment, money, and scarcity.
I'm hoping we get to the latter before the former.