Annie Lowrey asks:
But providing an alternative measure of what we produce or consume based on the value people derive from Wikipedia or Pandora proves an extraordinary challenge–indeed, no economist has ever really done it. Brynjolffson says it is possible, perhaps, by adding up various "consumer surpluses," measures of how much consumers would be willing to pay for a given good or service, versus how much they do pay. (You might pony up $10 for a CD, but why would you if it is free?) That might give a rough sense of the dollar value of what the Internet tends to provide for nothing–and give us an alternative sense of the value of our technologies to us, if not their ability to produce growth or revenue for us.
Here is much more.