For one, 4th is looking at property crime, not "most dangerous," where SF is #37 for violent crime. Yes, SF attracts the nexus of crime around the BART stops, but that also pulls it from most of the surrounding area, which OP was talking Bay Area as a whole.
Anecdotally, I've been here 30 years and never victim of a "dangerous" crime. Fat chance you move to Mountain View to work at Google and anything happens to you.
The only place in CA someone reading a "Best City for Techies" will encounter crime is Market St. and Tenderloin in SF. The rest of it in deep Oakland, Stockton, Modesto, San Bernardino, and pockets of LA, they will never end up.
I am pretty sure most people who work for Google and live in the south bay could tell you stories of having their car windows smashed in, and I do mean most. I think it is about 100% of the googlers and ex-googlers I know have had that experience.
Also as of two years ago, the chances that your Catalytic converter was stolen unless you parked your car in your garage was getting near 50% as well.
I suppose if you limit crime to just "dangerous" maybe it comes out on top, but I would prefer to be somewhere that I don't have to worry about 50,000 of my neighbors OD'ing on the street every year.
South Bay petty crime and homelessness has unfortunately arisen but that is a real alarmist way to speak about the most mundane stretch of suburban sprawl outside of LA County.
Interestingly, this is a similar experience I have from friends from when I lived in Johannesburg. Smash and grabs and car/parts thefts were very common.
