"... programs like TechStars — which engage the entire entrepreneurial community for 90 days a year — are the icing on the cake." - The icing on the cake is the important part. A lot of communities forget the base steps such as the meetups and the forums and they jump right to the funding. This limit the growth of the entrepreneurs and the community just as Brad discusses.
I like that Brad touches on the time-factor of 20+ years. I think it's easy to forget that it takes a long, long time to create a sustainable business environment, and it also takes years of success stories and phenomenal leadership to put a city on the entrepreneurial map. SV has made more than a few good tech companies. Hollywood has made more than a couple good movies. NY has made more than a handful of innovative finance companies. These legendary communities have created extraordinary results, but they didn't become legendary overnight.