Tech's center of gravity shifts north to San Francisco

The venture capitalist Vinod Khosla recently described Silicon Valley as a state of mind, rather than a geographical place. If that's the case, that state of mind can increasingly be found in San Francisco.

Young tech companies have been flocking to the city at such a rate lately that, in the words of Peter Wendell, founder of Sierra Ventures, in parts of San Francisco "you can almost go door-to-door." San Francisco, a short hop by train or car from the chain of towns that make up Silicon Valley, has long had some tech stars of its own. But the number of prominent tech startups that have opened new or expanded offices here lately is a break from the past. The technology center of gravity in the region seems to be drifting northward to San Francisco.