John Cole puts together what I think is a pretty accurate rationale for why BP is acting the way it is right now:

BP is just acting rationally, if you ask me. They’ve looked at the landscape, realize that even if they get sued for a shitload, the courts will strike it down as unfair, and they know they have nothing to fear from the government because both parties are littered with politicians they’ve completely paid off, and they know damned well that one major party wants to get rid of the EPA and the blue dogs in the Democratic caucus would join them, so they have no reason whatsoever to listen to that agency. Basically, the rational decision for any corporation in this country is to do whatever the fuck you want, because there simply won’t be any consequences. They have a lot of shareholders who will look the other way, a country desperate for oil, politicians completely in their pocket, and they can afford better attorneys than the poor bastards who used to catch shrimp in the Gulf.

Update: See below in the comments for more info on what I meant by the above. This post by Mistermix can also help add a little context:

The Economist:

The spill has so far cost BP $760m dollars. The company’s stock has fallen by a quarter. That was inevitable. What was not inevitable is the damage the company has done to its own reputation by continuing to lowball its estimates of the magnitude of the spill.

One of the beauties of being part of an oligopoly is that you don’t have to give a damn about your bad reputation. Sure, BP is going to have a few down quarters, and they’ll spend millions on ads and re-branding. But they’re not in any kind of mortal danger, in part because oil is a commodity where brand doesn’t really matter, but mostly because the sound and fury being emitted by Congress and the Obama Administration will amount to nothing.