How many of those stockholders are going to affected by the local impact to Louisiana and the possible National/Global economic impact as it radiates outward? It's short-sighted to talk about BP's obligations to their stockholders just in terms of raw stock prices.

[ You also fail to mention that many BP employees as well as executives and board members probably have stock options, meaning that they are also looking after their own interests in this matter too. It's not like they want to be altruistic, but these pesky investors are holding them back. And it's not like these 'stockholders' are some external entity to the company with a hard line between investors and employees with no grey area in between. ]

{edit} AIG also had an obligation to their investors to keep the stock price up and up and up... until it came crashing down. Saying, 'they have an obligation to their investors,' is really just a cop out. It's a way of pushing responsibility away (i.e. "Don't blame me! I have a responsibility to the investors, my hands are tied! I'm compelled to this course of action.").