Tech Buoys San Francisco

San Francisco is enjoying a renaissance as a technology center, as numerous Web and digital-media companies move in or expand in a burst of economic activity not seen since the dot-com boom of the 1990s.

While there has long been plenty of high-tech ferment 30 miles to the south in Silicon Valley, San Francisco itself has traditionally been the region's finance and cultural center rather than a tech magnet. Now, the city is seeing growth from start-ups such as micro-blogging service Twitter and social-gaming company Zynga Game Network. At the same time, the city's design talent, cheaper office rents and mix of amenities are drawing an influx of smaller tech firms, such as social-gaming start-up Booyah Inc. and help-desk software start-up Zendesk. It isn't clear how sustainable San Francisco's tech boom is, though, especially since start-ups are by definition unproven. Many of the Web-based ones aren't yet generating revenue, much less profit. And most rely largely on the same cadres of venture capitalists, so if funding dried up, the impact would be widely felt.