1950-2000 was one of those rare moments in history when industries (whole states, countries even) could coast on regular, incremental improvements to a single world-changing technology. SV was in the right place at the right time, and never totally lost it's edge. But the semiconductor and software industries are mature now, and spread much more widely than thirty years ago. SV still retains many advantages, but you can't get blood from a stone. The radical, disruptive stage of digital technology is over.