A board of directors has significant discretion in deciding what course of action truly maximizes the long-term value of a company; see the business judgement rule, for instance ( http://en.wikipedia.org/wiki/Business_judgment_rule ).

The flippant view that a board is obligated to maximize profit (especially short-term profit) is pretty simple-minded. See also http://crookedtimber.org/2008/07/24/fiduciary-obligation-vs-... and http://crookedtimber.org/2008/07/25/what-obligation-maximise...