If the new units are primarily owner-occupied, NIMBY-ism is a risk. If the new units' residents are renters on 1-year leases, they would probably vote for ever increasing supply.

Yes, this. I've often thought that in terms of long-term strategy, pro-housing groups should focus on getting rental housing built, and leave owner-occupied condos alone.

I confess I've wondered how many of the San Francisco residents loudly blaming the influx of tech workers/startups for the spiraling housing costs there, and (2) moved to the SF Bay Area during the first dotcom rush.