South Park is here to explain it to you.
The foul mouthed cartoon, which never passes up an opportunity to make fun of the government, recently aired a hysterical episode parodying the real estate collapse. The episode's called "Margaritaville," and can be viewed for free here.
Love 'em or hate 'em, you gotta hand it to creators Trey Parker and Matt Stone- they sure know their metaphors.
(For anyone who doesn't get the sarcasm- substitute the world "margaritaville" for house.)