If there is evidence that all no-doc loans are bad loans, then that is a regulatory problem and a gray area for people to walk on. The government should pay attention to it and to correct it.
For owners, buying a house is a big deal. Of course one can always complaint about others not telling them in advance. These people are adults. But if one do not think they can afford a house at certain price yet they still buy it with all sorts of exotic loans, then I think these owners have more to be blamed. Further, once they hook on the financial responsibility, they have the obligation to commit the it until it ends. House price always goes up and down, it is like investment. If these people are buying a house to live in, who really cares about the up and down and the fluctuation of the market should not really affect their lives. But these days, buying houses or walking away from houses becomes a fashion and everybody is just doing what other people are doing without considering the consequences. These are the people to blame.
Besides, this is an issue of morality. If they think that it is easy to get a loan and easy to give up their responsibility, then they can do the same thing to a car loan or any other sorts of loan and they can walk away without further thinking. This attitude will create financial chaos not only to these people but to other people that are more financially responsible, such as tax payers like us.