The sky over San Francisco is cerulean blue as you begin your descent into the city from 2,000 feet. As you pass over the southern hills, the skyline of the Financial District rises into view. On the descent into downtown, familiar skyscrapers form an urban canyon around you; you can even see the trolley tracks running down the valley formed by Market Street. But then a little pop-up box next to the Bay Bridge explains that an accident has just occurred on the western span, and a thick red line indicates the resulting traffic jam along the highway. A banner ad for Emeryville, Calif., firm ZipRealty hangs incongruously in the air over the Transamerica Pyramid. You are actually staring at your PC screen, not out an airplane window.