[oneJob]

Before Silicon Valley gets all flattered, consider:

"Soifer has long studied the proportion of Harvard MBAs who pursue careers in finance; when more than 3 in 10 head for Wall Street, it's time for investors to sell, he says."[1]

I used to work on Wall Street. I left because of this issue writ large. There are quite a few pieces of research claiming this trend is a negative indicator.

[1]http://www.cnbc.com/id/45030885

[chad_walters]

Likewise when they start heading to Silicon Valley in droves... Last time around was 2000 -- 'nuff said.

[wpietri]

I can't find the reference, but I recall there being a similar phenomenon with real estate agents. During booms a ton of people flock into the field, increasing the problem and hastening the crash.