> If I had money to own or build, I certainly would be disincentivized to build if I knew those properties could become rent controlled.

You live in SF, so you know that new construction will not be covered under rent control laws. [0] Why would you say this?

> But gov't needs to encourage building, not stifle building, which seems they work very hard at.

Agreed.

If the city government removes the anti-development zoning laws in much of the city and works to placate the rabid anti-development leaders in both the "DON'T SPOIL MY VIEW!" and "NEW CONSTRUCTION IS ALWAYS RENT CONTROLLED UNIT DESTRUCTION AND YOU SHALL NEVER DESTROY A SINGLE RENT CONTROLLED UNIT!" camps, and there is still barely any new construction, then perhaps it will be time to see why a law that controls rent only in buildings constructed prior to 1970-mumble is stifling construction of new buildings in 2015.

[0] Except in special cases like the Trinity Towers project. In that case, Sangiacomo got permission to destroy a building full of rent controlled units if he replaced each of those units with a rent controlled one in the new building. This was a 1:1 replacement. No rent controlled units were lost, no additional rent controlled units were created, and Sangiacomo got a new building full of "market rate" units in the bargain.