The objection I often hear (and I recall that this is PG's stance as well) is that as old jobs disappear new ones will take their place. For example, as the article mentioned, the former toll booth operator could now repair the automated toll booth system.
So far this general idea has been true. Before computers existed as we know them, "computers" were people who did lengthy computations for a living, often for scientists. Once electronic computers arrived these people seemingly found new jobs and survived.
I'm not sure if this will continue to be the case. We may be reaching a discontinuous point on the economic timeline. If robotic and computer systems are developed that can effectively do the jobs of most humans for less than minimum wage, there won't be enough work for people to make a good living.
The key difference is the following: in the past, technology has only disrupted specific segments of the economy, allowing humans to find work other places where they could still add value. Now, technology has the potential to disrupt the majority of the economy. There won't be any work to do.
There will still be pockets where humans can add value, but there will be so much competition for this work by all the unemployed that the wages will be driven down to nil.
If this situation occurs, the Government will have to find a way to distribute resources directly to the masses lest every sitting politician be voted out of office. In fact, all the rhetoric right now about creating jobs is exactly that. Politicians are promising that they'll find a way to distribute resources to the unemployed.