Market cap only represents the value those tech companies have managed to capture, though. I rarely click on Google's ads and therefore contribute little to their market cap, but access to search engines like Google has had a tremendous impact on my life.
Although the US didn't capture all of the losses from the War on Terror, either!
There's a long article in this week's The Economist:
The onrushing wave
discussing the effect of changing technology upon the amount of employment available in different sectors of the economy.
Sample paragraph from it:
(There's a summary online of their previous book: Race Against The Machine: How the Digital Revolution is Accelerating Innovation, Driving Productivity, and Irreversibly Transforming Employment and the Economy)
What do people think are society's practical options for coping with this change?