Incumbent property owners benefit immensely when you must seek government permission to build on your land (to what standard: different conversation).

In then end, they are gonna shoot themselves in the foot as the big tech companies become rational and move away from san francisco toward more reasonable growing cities like Denver.

Here's a study that demonstrates the control existing homeowners have over zoning policy: http://cityobservatory.org/homevoters-v-the-growth-machine/