In the New Yorker, James Surowiecki looks to Erik Brynjolfsson and Andrew McAfee's forthcoming book The Second Machine Age: Work, Progress, and Prosperity in a Time of Brilliant Technologies for a discussion of one of the major problems with using GDP as a means of assessing the economic health of a nation. Because GDP uses the dollar-value of all transactions as a proxy for economic vibrancy, it discounts to zero any productivity improvements that result in expensive things becoming free. For example, if every technology company has to license a Microsoft operating system for every one of its servers and products, that's great for GDP: it adds billions to the national bottom line. But when GNU/Linux comes along and zeros out the cost of operating systems for your data-center and embedded systems, GDP drops.
But the impact on the nation is a net positive: first, because existing products get cheaper as they no longer include a Microsoft tax; second, because new products and services emerge that would not have been profitable/possible with the Microsoft tax included. It's not great for Microsoft, its employees, suppliers, and shareholders, but their pain -- which is real and terrible -- is dwarfed by the wider benefit.