It helps that there's no margin calls. If anything, in many states you can just send jinglemail and only be out the cash you've put down while the RMBS holders scramble to recoup whatever they can with a house they never wanted to have to sell -- usually amid a falling market.
The way risks are distorted by the political machinations of the mortgage industry makes it pretty painfully obvious why the housing market is such a mess. And then they have the audacity to blame expensive housing on "capitalism."