[shapefrog]

Also (for non-recourse state):

House cost: $200,000

Down Payment: $10,000 (5%)

(Time passes...)

Value at foreclosure: $100,000 (massive change)

The bank sells the house for $100,000. You don't get your $10,000 back. But you're not on the hook for anything. You walk away minus $10,000 (i.e. 1x) and a hit to your credit. You went from owing the bank $190,000 to owing $0.

[runako]

Exactly this. If the property goes up $100k, you earn a 10x return on your $10k. If it goes down $100k, you only lose your $10k (in non-recourse states). It's asymmetric leverage.