This canard keeps getting repeated on HackerNews.
It's not 2011 anymore, when housing construction was at its lowest because of the overhang due to the massive real estate bubble.
It's 2013 and a construction boom is under way that is so large that in the next 2 years more housing will be built than in the past 15 years combined.
http://www.bizjournals.com/sanfrancisco/print-edition/2013/0...
That said, it's great news that so many rental units will be made available in the next few years.
How many units were built in 2006, 2007, and 2008?
figure 3 on page 11 illustrates the point I was making:
http://www.sf-planning.org/ftp/files/publications_reports/20...
Look at the price of housing from 2007 to 2011, and if you understand the role of price in marketplaces, you'll understand why construction was so low.