First off, the author misrepresented some facts. Groupon is NOT profitable. Nor is Pandora or Zynga, and Linkedin trades at roughly 900 times earnings. And I suppose this is a matter of debate, but I severely disagree with his depiction of these as stable companies. Pandora is operating in an ultra-competitive market with razor-thin margins and enormous overhead. I personally doubt they are going to survive much longer. I'll go out on what some would consider a limb and put Zynga in the same category, albeit one that will survive a bit longer.<p>But to his point about a possible bubble- I think it all depends upon exactly how you define this thing we call a bubble. If you compare the climate of today's dot com startups with that of the 90's, certainly we are nowhere close. Very few internet companies are going public these days, and those that are aren't enough to create a bubble large enough that a collapse would mean more than a microscopic percentage of the market at large losing a substantial amount of money. Most employees are not paid entirely in stock, so you wouldn't see a whole class of people go from millionaires to penniless in a matter of days.<p>However, if you define a bubble simply as a disproportionately large number of businesses in a particular industry being obscenely overvalued, I think we've been there for a few years. I don't think it will end abruptly from a string of bankruptcies or a market crash like the last one. I think it will end when the market becomes sufficiently saturated with businesses creating such a small amount of value that other industries become more attractive for investment. When the money leaves, people will pursue businesses in those industries.