Nothing personal, it's just business.

If I were significantly underwater, decided it was time to move on, and found a workable alternative then I would jump ship and default too. Everyone wants a piece of your money and sometimes you have to wrap your arms around it and hoard it for yourself to get through a tough time. I like where I live and don't want to do that. However, there may come a time where it becomes the path of least resistance to jump ship.

Real estate is an investment regardless of how many people say it's not. Businesses treat it as an investment. People put their money towards a mortgage hoping for free and clear ownership in the future or a significant bump in value just like a stock or some other investment. Real estate can be a way to move up in status just like stocks or other investments. I see no moral or ethical problem for people who default and turn over their real estate without trashing it. They are simply following the contract. It's not their fault the big banks didn't plan for the worst. Those who trash their real estate on the way out should face heavy consequences though.

Would I prefer people to honor their obligations despite the out clauses? Yes. That's just not the way things work these days. If you don't cover your own butt you risk getting taken advantage of.