As you may have heard, the Fed has recently ended its mortgage-backed security buying program. Furthermore, Bank of America is increasing the foreclosure rate of its properties, from 7,500 homes a month nationally, with the goal to increase that number to 45,000 homes per month by December of 2010. On top of that, there's evidence of increased strategic defaults, and the $8,000 first-time homebuyer credit is about to expire.
All these factors, combined, appear to have created a perfect storm in the housing market. Just in the last month alone, all San Diego sub-markets crashed 10+% across the board, and it looks like the decline will only accelerate from this point on.