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NEW YORK — VCs continue to invest irrationally, Spark Capital partner Dennis Miller said at EconAds yesterday. He said too many VCs invest in "rock star" founders as though they are "a call option on a bright future." Others too quickly buy the hype from hard-selling founders. Too many company's are getting too high valuations, he added.

I think exits are much bigger question mark today then they were 6 months ago. Think of the exits Ning, and Brightcove have to get to make their investors happy. It's a daunting, daunting number.

Of course, Miller happily ignores his own advice. Spark just valued Twitter
— a company with no business model and no reliability — at just under$100 million, leading a $15 million funding round. This guy's almost as funny as his comedian namesake.