Let's not forget: AirBnB isn't helping either. No, not the AirBnB employees; but the loads of people renting out their spare rooms, when earlier they would have taken in a roommate. I just checked, and 2300 listings came up for San Francisco.

Plus, SF Tenants Union is very powerful. Once you are a renter, you can basically do anything and the landlord can't kick you out. Consider this example from today's paper: http://www.sfgate.com/bayarea/article/Landlord-nightmare-in-... . As a result, some people are leery of renting.

In other words: while the demand has gone up, the supply seems to have come down.