Precisely five years ago, I explained to TechCrunch readers that I had grown bored with San Francisco.

By which I really meant Silicon Valley. As I surveyed the tech industry landscape circa March 2011, I saw a financial boom but a creativity bust. The star companies of that year – the Instagrams and Quoras and Paths – might have been worth hundreds of millions (or even billions) but they offered almost nothing in terms of innovation or revolution. In fact, the entire tech industry seemed to have lost its courage; its revolutionary zeal...