This, in a nutshell, is the controversy that we'll see played out repeatedly over the next few decades, as production costs are driven to zero by rapid technological advances. The recording and movie industries were unlucky enough to be caught first - their product is easily digitized, and their costs are almost entirely fixed costs so they're forced to make up the difference by increasing the unit price to well over the marginal cost of a unit. As a result, you can get their products for free online, and it's costing them heavily (though, that's debatable, and they may survive yet if they're smart about it). But, they certainly won't be the last industry to be caught. Robotics is a pretty primitive field right now compared to what it could be; if it were to reach its potential I don't think it's unreasonable to assume that 80% of the people in the world could be put out of work.
What do we do then? I suppose I mean that question in two senses. First, what do we do with society? Some kind of massive socialist state is probably what we'll end up with, but it's not at all obvious that that's the best solution. (What do you guys think?) Secondly, what will we do individually? High-tech jobs will obviously still be in demand, but there won't be all that many of those. Maybe we'll see an explosion of creativity, of art and literature and all that neat stuff, but that's really not for everybody. What will we have to offer the people who need a sense of purpose, the ones that would never be satisfied with a techno-utopia where nothing really needs to be done?
Some of you will say that I'm guessing way too high on my 80% figure, but don't be too sure. Unskilled manual labor will be the first to go, and indeed, that's already happening in some places - witness the mechanization of the auto industry, and how few workers they actually need in the factories these days. This will become the norm over time, and after a while automation will make inroads in more specialized areas as well. The wonderful/terrible thing about technology is that it only moves in one direction. Once an advance is made, that ground is never given up; the trends that accompany technology are stark and to some extent unstoppable. The genie's out of the bottle, and we need to stop trying to push it back in, and start making wishes, already.