From the MR comments:

http://lesswrong.com/lw/hh4/the_robots_ai_and_unemployment_antifaq/ (Tyler, have you read that?) I don’t actually get Brynjolfsson and McAfee. I read the original book and it seemed very unoriginal and not to address at all the basic question of “Why did Ricardian reemployment work fine when agricultural jobs went from 95% to 3%, work fine when automobiles put the whole horse-and-buggy industry out of existence, work fine when women entered the workforce during WWII, and then suddenly stop working?”

The Ricardian comparison is the technology-relevant one here, and I would challenge the notion that it went fine. Think of the machines of the industrial revolution as getting underway sometime in the 1770s or 1780s. The big wage gains for British workers don’t really come until the 1840s. Depending on your exact starting point, that is over fifty years of labor market problems from automation, and yes it is correct to also blame various bad laws, mobility restrictions, wars and taxes, and the like. Even Ricardo, very much a free market economist, worried about the machinery question in his day and rightly so. The industrial revolution was a wonderful development with huge ongoing gains, but still it did bring some very real adjustment issues.

A second point is that now we have a much more extensive network of government benefits and also regulations which increase the fixed cost of hiring labor. Insofar as automation creates short-run adjustment problems, those problems are more likely to show up in the form of decreased labor force participation than they did in previous eras. We are living in a time where the long-run trend is for labor force participation to fall in any case, and that was not in general the case during those earlier episodes.

You also might try to run with a “back then machines substituted for brawn, now they are substituting for brains” argument. Maybe so, but you don’t even need to make that work to have a substantial (non-Luddite) worry.