Silicon Valley 'rapidly becoming bipolar': PayPal co-founder

In the technology world, no question comes up more frequently these days than "Are we in a bubble?" And while it's not up to us at CNBC to answer that question, we do sometimes happen upon little nuggets—data, anecdotes, tweets and the occasional wild partythat can possibly help others make their own assessments. When we do, we'll share them in an occasional column we're calling "Bubble watch?"

The start-up tech world is seeing a series of undeserved valuations, according to one of Silicon Valley's biggest entrepreneurs.

Max Levchin, PayPal co-founder and Yelp chairman, told CNBC that some of technology's biggest recent successes are deserving of their billion-dollar valuations, but others are simply riding those coattails to inflated assessments.

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"I think Silicon Valley is rapidly becoming bipolar," he said, explaining that many investors are overpaying for companies that may not pan out.

"There are some amazing runaway successes such as Uber, or even Twitch [recently acquired by Amazon], that are just truly one of a kind, very valuable. And what valuations investors are putting on them—that's a liquid market, people are paying the premium that they deserve," Levchin said.

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"There's also a whole bunch of companies that are drafting off of valuations that absolutely do not deserve those kinds of numbers, but because some giants like these exist, they can enjoy the valuations," he added.

—By CNBC's Everett Rosenfeld