I'm not sure where you're getting your information that the majority of promising startups are in the South Bay. The energy in Silicon Valley has been shifting

I'm not sure where you're getting your information that the majority of promising startups are in the South Bay. The energy in Silicon Valley has been shifting northwards for the last 10 years. The majority of large companies are in the South Bay, but among companies less than 5 years old, there are as many great ones in SF as in PA/MV.