Also another possible reason why someone in CALIFORNIA can 'walk away' is that there is no personal liability on a 1st mortgage.... NO BOND
Where I've live/lived [east coast] when you take out a mortgage you also have to 'personally guaranty' the loan with a 'BOND' . The mortage is secured by the real eastate, but the bond makes the loan a personal obligation.
So if you don't like being 'upside down' you can merely throw the keys bank to the lender and walk away with impunity! May give you a 'blemish' on your credit report but thats less costly than paying real cash!
Hmmm...strange, I don't think that's the case down here in Florida...could be wrong, but I don't remember any "bond". IMHO, that's the way it should be though.