Is it unethical to allow your house to be foreclosed?

I just heard on the news that many people whose houses are worth much less than they paid for them have stopped making payments in order to have the bank foreclose, so they can buy a new house and make smaller mortgage payments. The news announcer said that many more people might be doing this except that they view voluntary foreclosure as unethical. Is it?

Should voluntary mortgage payment default be viewed as breach of contract? Could it not be said that foreclosure in response to non-payment is built into the contract and that the home owner is just exercising an option in the contract?

Suppose we extend this idea. Is civil disobedience really disobedience? Instead of viewing a law as saying that you must or must not do something, could it not be viewed as providing an option? You can either refrain from robbing banks or allow yourself to be imprisoned. By openly carrying out certain acts and willingly accepting the consequences, doesn’t this make you compliant with the law?