"What’s needed is for a critical mass—say Google and Apple and Facebook and Twitter—to move all at once, to the same place, thus immediately creating a new tech

"What’s needed is for a critical mass—say Google and Apple and Facebook and Twitter—to move all at once, to the same place, thus immediately creating a new tech hub." Most of the millionaires who cashed out of those companies have already left, and many others would be unwilling to relocate. I don't think moving the ecosystem of angel investors etc. which powers the valley is so easy.