Going for 7 years doesn't prove it's not a bubble, especially when many of the externalities people have suggested are causing a bubble have not changed (low interest rates, for instance).
It's more like 10 years if you include Facebook - that's an entire business cycle, or about the same duration as the 1990-2000 internet boom. But in siding with Andreessen and others, I think this one has further to run.
Its not a business cycle, really. The fed last week said the stock market will crash if they put interest rates much above zero. That is the definition of a bubble. A bubble is a mis-pricing of risk based on non-market force (irrational or otherwise) that will revert to equilibrium when given the chance.
But I am pessimistic about the hardware unicorns (fitbit, skullcandy, jawbone) as opposed to the app/website ones, so It's not like I am emphatically bullish about everything. http://greyenlightenment.com/billion-dollar-startup-club-pic...