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 party—that 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.