Theranos, Juicero, Ubeam, Y combinator flying motorbike, Airware, Jawbone, pretty much any "AI" or even machine learning company that isn't overtly a consulting firm, pretty much any autonomous vehicle startup that isn't a mapping company.... Most of the companies which have "succeeded" in the post-2008 landscape have been pretty feeble; it's not like Uber or AirBnB are tech companies. They're phone apps that enable people to defy taxi and hotel laws.
FWIIW I've known Byrne for years, and was shocked when he moved to the Bay Area.
Like I said, mistakes happen. Investors in the valley are willing to take larger risks, and by virtue of there being more money, there will be more mistakes. There are mistakes in Boston too. I don’t know the statistics, but I would bet it’s proportional, though perhaps not because the risk appetite is lower.
Twilio, Stripe, Pure Storage, Nutanix, Slack, Dropbox, Box, SpaceX...
Some of these companies could never have started in Boston, because finding capital would have been impossible. It isn’t always technological advantage that wins, but UX or biz model, or any number of other things related to execution.
FWIIW I've known Byrne for years, and was shocked when he moved to the Bay Area.