Certainly that is problem, however the vast majority of homes in California are owned by home owners not speculators. Anybody know the percentage of owner occupied single family houses in the US and/or CA? Obviously, the folks with lousy credit, faced with reseting higher interest rates, and zero equity are going to walk away. There is a reason they have lousy credit scores they don't pay their debts.
For the far more typical case of a home owner with decent to good credit who bought recently with only 10% down their equity maybe close to zero, and their teaser rate is expiring. The decision to walk away isn't something to do lightly. They still need someplace to live and they don't want to ruin their credit. Finally, despite all the hype about lousy loans, plenty of home loans are still made where the home owner puts down 20% and borrows money at a low fixed rate. These folks aren't walking away.
Wachovia and Countrywide made a lot of loans to the first type of borrower, Wells Fargo made loans to the second type. The difference are pretty significant WFC had 32 million charge of on a 71 billion mortgage loan portfolio. Wachovia has a much worse track record with 1.5 billion in charge offs.