In the three years that marked the height of the last boom, 1999 through 2001, the VC industry sank $96.4 billion into web start-ups, with more than 80 percent of that or nearly $78 billion in the United States alone, the Thomson Reuters data show. Of 10,755 VC deals over that run, 7,174 took place in the U.S. market.

Not so today. Of the more than $5 billion of VC money invested so far in 2011, just $1.4 billion has been deployed in U.S. start-ups. according to Thomson Reuters data. Roughly three quarters of the 403 deals have taken place overseas.