This is a condition affecting SFO more than other airports, and is due to the frequent condition of low clouds/fog/drizzle combined with parallel runways too close for simultaneous approaches during these weather episodes, and there's a related thread in the San Francisco forum
http://www.flyertalk.com/forum/san-f...thers-not.html
I'll move this to that forum for more discussion. Ocn Vw 1K, Moderator, TravelBuzz.