There aren't /that/ many tech people moving to Silicon Valley, though there certainly are a lot. What are you going to do about children who grew up in California and can't live in the same city as their parents? There isn't even enough supply for them.
One of the worst aspects of prop 13 is that the property tax cap is hereditary. It's outrageous and creates a real risk of an honest-to-god blood-based class divide in the region.
