Best summary of bubble/non-bubble debate I've read yet:<p>“Maybe,” says Naval, “Certainly valuations are creepy up quickly in all stages of deals. On the other hand, 10 years ago when we all felt like this last time the total market size for any company was at maximum 100 million potential users. Now we’re in the billions of users. Facebook connections alone bring 500 million, Twitter 200 million. 10 years ago we only connected for brief periods of time when we were at our PCs. Now we’re connected to apps all the time, everywhere we go. So maybe there’s a bubble. It’s hard to say. But we’re also looking at unprecedented opportunity.”