From the title I was assuming it was going to be an article about Detroit or some other place where there really is no possibility of house prices falling becau

From the title I was assuming it was going to be an article about Detroit or some other place where there really is no possibility of house prices falling because they are already at or near zero. In SF falling prices is definitely possible even if not likely in the short term. If the acquisitions and other positive exits dry up (even for a couple of years) the prices may readjust quickly and once they start to fall the perception of inevitably rising prices will disappear taking further demand with it (people will prefer to wait for cheaper prices rather than buying urgently before prices rise further). I am not predicting immediate falls by any stretch but when people start saying prices can't fall is when people buy on that basis and are shocked and damaged when they do (which at some point they will).