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A Twitter tweet announcing the company's planned initial public offering (IPO) is pictured on a mobile telephone back-dropped by various twitter logos on October 4, 2013. A new book out details the sometimes-sordid history of how the social networking company got its start.  - 

It might be an understatement to say that investors are pumped up about social networks and other tech companies. And the numbers are eye-popping. Twitter: valued at $11 billion. Pinterest? $4 billion. And the list goes on.

If all of this makes you feel a bit of queasiness and déjà vu, you're not alone. Lots of people are talking about the dot-com bubble of the late 90s -- and, boy, did that bubble pop. Should we be nervous?

Marketplace Host Ben Johnson speaks with Lindsey Turrentine of CNET. 

Follow Ben Johnson at @@TheBrockJohnson