Intel cleanroom workers in their bunny suits.
Loss: $400 billion
Peak market cap: $509 billion (August 2000)
Recent market cap: $109 billion
Like Cisco and Microsoft, Intel has long been a successful company -- albeit one that couldn't live up to insanely high expectations. When the stock hit its peak in August 2000, analysts "scrutinized Intel's pronouncements as meticulously as they parsed the syntax of Federal Reserve Chairman Alan Greenspan," as a 2003 UCLA study put it. A month later, Intel trimmed its growth forecasts, sending the stock into a free fall from which it never recovered.