I remember taking the light rail everyday in North Sunnyvale on Java Drive a few years ago, and wondered why companies like Google, Facebook, etc didn't move over there-there were so many vacant buildings, all next to VTA light rail. Apple's campus has mediocre bus service (VTA 55), Google's has practically none I can think of (piss poor location for transit) and FB is banking on the unicorn-like hope of revitalizing Redwood Junction and building a Caltrain spur.
I bet dollars to doughnuts most people who work at big name tech companies in Santa Clara County, and who actually live in Santa Clara County, drive to work.