When a private individual walks away from an underwater mortgage because the deal suddenly sucks, they're seen as a scum-bag leech whose word isn't worth dirt. Get the economic-justice crowd in on the discussion and they start bandying about "debtor's prisons" and erecting straw-men for the dead-beat bonfire.
But when a bank walks away from an underwater property because the deal suddenly sucks, they're seen as smart. Shrewd. Walking might even be a bonus-worthy decision.
Not that private individuals are incapable of screwing one another over and somehow dodging social judgment [1]. It's just far, far less common. And the best treatment they get is a polite look in the other direction. No-one's printing an Op-Ed celebrating those decisions and castigating any attempts at socio-moral critique.
[1] For some reason we all look the other way when it comes to immigrant au-pairs. And that's horrible.
That said, mission effing accomplished for the company: they're well north of a million dollars richer because good little kids don't drop their drawers or talk salary numbers. This topic makes me feel positively Marxist: we're willingly participating in a system designed and perpetuated to exploit us because to do otherwise would be impolite.