Social media is driving what appears to be another dot-com bubble as investor enthusiasm for such properties as Linkedin, as well as start up companies is driving billions in investment.

Will it be different this time? Reuters:

* Online advertising and e-commerce, in their infancy a decade ago, have matured into accepted and more reliable revenue sources

* The rush to cash out through an initial public offering has slowed. Bountiful sources of private investment, a raft of new public company disclosure regulations and the growth of alternative venues for trading private company shares provide the means and incentive to delay going public

Perhaps the most distinguishing factor from the "It's different this time" litany is that today's web frenzy is global.

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.

The dollar amount should raise a few eyebrows; $5 billion in the first four months of 2011. This doesn't approach the $55 billion poured into start ups in 2000, but if it continues, this year will be the biggest year since then.

No doubt most of the start ups will fail - that is the nature of business. But those putting their money into this market are hoping that the next Facebook or YouTube will emerge and reward their risk taking.