A minimum 3-story building with underground parking requirement for all new commercial construction would go a long way towards fixing all of the land shortage in the Silicon Valley area.
Not really possible. Apple had to get a special waiver from Santa Clara to build the 6 4 story buildings on their Infinite Loop campus. They are actually configured structurally to be 5 story buildings, but the additional waivers fell through at the last minute, so they were stuck with 4 (while everyone else is stuck with the statutory 3). Santa Clara and San Jose don't want tall buildings.
That said, the folks I know who live in SF live there because there's nothing for them to do in the SV area. Being young, they like being able to walk from their apartments to the hottest clubs or concerts or whatever. Most of those folks move back out to the suburbs by the time they have their first kid, but there's always a new batch of youngsters waiting in the wings to take those apartments when they leave.
They practically roll up the sidewalks in SF at 9PM. If you want late night food, you have to go to some place in the Castro, a club that serves food (assuming they let you in), a bar (kitchen usually closes at 10), or go to the waffle house, Denny's, Mel's, or one of a couple (mostly take-out) pizza places.
If you are doing dinner and a movie, you pretty much have to do the dinner first, or nothing will be open after the movie lets out.
People erroneously think SF is a metropolis, like NY - it's not. By that standard, there's more late night food places in Ogden, Utah, than there is in SF.
So unless you are an alcoholic or a "club kid", you are not living in SF for the thriving night life.