San Jose/San Francisco/Silicon Valley
Unemployment rate: 10.3%
Largest employers: A patchwork of technology companies
If any community knows just how quickly the tech tide can turn, it's San Jose. After the tech boom of the late 1990s pushed the Nasdaq to 5,132.52 in March 2000 and its subsequent collapse drove it to below 2,500 by that December, Silicon Valley high-tech industries dropped off by 17% and roughly 85,000 jobs just disappeared by 2008, according to the Bureau of Labor Statistics. Jobs in the Internet community, telecom and data processing alone declined 26% between 2000-08.

San Jose, San Francisco and the rest of Silicon Valley are bracing for Round 2 as companies such as Farmville maker Zynga, business networking site LinkedIn and even Twitter are IPO gossip fodder while even mainstays including Google ( GOOG), Cisco ( CSCO) and Intel ( INTC) are eyeing advances by Apple ( AAPL) and purchases by Microsoft ( MSFT) before making their next move. Though the amount of venture capital flowing in for the little guys last year is less than a quarter of the $8.5 billion that came rushing into Silicon Valley at the peak of the tech boom, according to Thompson Reuters, Tesla's ( TSLA) IPO last year, the rising star of Facebook's still 20-something Mark Zuckerberg and the renewed presence of big money and big risk in the air still has locals and some investors nervous.

It's hard to blame them, as even in the new "good times," unemployment's still more than a percentage point higher than the national average. If the latest tech surge goes south, the guys with the Lamborghinis could add a lot of staff to that percentage.

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