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San Francisco's tech boom 'changing the soul of the city'

31 January 2014 Last updated at 11:12 GMT

The centre of the technology world has traditionally been Silicon Valley in California.

But 30 miles north, San Francisco is now home to a staggering 2,000 tech companies, including the likes of Twitter and Instagram.

Some say it is "changing the soul of the city".

Richard Taylor reports.