This is a purely ad hominem argument. His arguments can be assessed on their merits, you shouldn't dismiss them because of who he is. And his central point see

This is a purely ad hominem argument. His arguments can be assessed on their merits, you shouldn't dismiss them because of who he is. And his central point seems to me to be pretty good: in a bubble like the 97-00 bubble, you'd expect newly IPO'd tech stocks to be soaring, not sinking. It doesn't appear that's happening. There's a different question which is whether two or three specific companies (Facebook, LinkedIn, Twitter) are overvalued right now. But even if they are, that's not really evidence of a tech bubble unless tech stocks in general are overvalued.