The high-tech revolution that began in the final decades of the 20th century is once more gaining momentum. The Nasdaq Composite index is approaching its heady heights of March 2000—except this time the bull market in high-tech shares is being driven by profitable companies with proven business models. More to the point, the changes wrought by the IT revolution are starting to cause social disruptions that may eventually prove even more severe than those of the industrial revolution 200 years ago.