> They have extra units in their building (which is also where they live), and choose to leave it vacant rather than deal with the hassle of rent control.
Good for them. Better that they do this than take the rental income, and later whine about how terribly unfair renter protection laws are. :)
Based on my immensely scientific[0] survey of Internet Message Boards (and personal experience in the American Southeast), it seems that potential landlords sometimes forget that when they rent their property to others for use as the renters' home, the landlord loses almost all control over that property. This is right and just: everyone deserves a safe, secure, private place to live.
> Leaving units vacant is a rational way of dealing with SF's condo conversion laws.
Again, it's good for the landlords that they showed this much restraint.
The condo conversion laws prevent landlords from turning their apartment stock (that pays off smaller amounts over time) into condo stock (that pays off one large lump sum). These are sane and rational laws to have in cities that (for a variety of disgusting reasons) find themselves unable to create sufficient housing to meet demand.
[0] Ha!