The Economist:

INNOVATION, the elixir of progress, has always cost people their jobs. In the Industrial Revolution artisan weavers were swept aside by the mechanical loom. Over the past 30 years the digital revolution has displaced many of the mid-skill jobs that underpinned 20th-century middle-class life. Typists, ticket agents, bank tellers and many production-line jobs have been dispensed with, just as the weavers were.
For those, including this newspaper, who believe that technological progress has made the world a better place, such churn is a natural part of rising prosperity. Although innovation kills some jobs, it creates new and better ones, as a more productive society becomes richer and its wealthier inhabitants demand more goods and services. A hundred years ago one in three American workers was employed on a farm. Today less than 2% of them produce far more food. The millions freed from the land were not consigned to joblessness, but found better-paid work as the economy grew more sophisticated. Today the pool of secretaries has shrunk, but there are ever more computer programmers and web designers.
Remember Ironbridge
Optimism remains the right starting-point, but for workers the dislocating effects of technology may make themselves evident faster than its benefits (see article). Even if new jobs and wonderful products emerge, in the short term income gaps will widen, causing huge social dislocation and perhaps even changing politics. Technology’s impact will feel like a tornado, hitting the rich world first, but eventually sweeping through poorer countries too. No government is prepared for it.