The ever-calculating consequentialist is incapable of commitment, and is thus deprived of a good life (which arguably requires stable life projects, relationships, etc.). So we shouldn't want people to be ever-calculating. Still, even when consequentialism is understood only as providing a criterion of rightness, rather than a decision procedure, the threat of alienation remains. According to maximizing utilitarianism, we are obliged to sacrifice our own lives and interests entirely, becoming (say) an aid worker in Africa if doing so would in fact bring about the greatest net benefits.
But perhaps it wouldn't. Worries about excessive demands aside, it seems plausible that some greater degree of self-investment is required for many to maintain their capacity to create value in the long term. Pure altruism is unsustainable; as human beings we need our personal projects and relationships. Like they say on airplanes: it's only once you have your own oxygen mask secured that you're in a position to help others. Moreover, it is largely through these personal commitments that we succeed in bringing value into the world!
Still, as Vanessa points out to me, this is not enough to get one off the hook. Even granting the necessity of having life projects, we can go back a step and question one's initial choice of vocation. Maybe it would do more harm than good to wrench a person off their established path, but we might still say that they ought to have chosen a different path in the first place. (Compare Unger's claim that young philosophers should go off and become rich lawyers instead -- effectively farming themselves for charitable donations. Ben Miller is similarly skeptical of the value of philosophy.) If one could form a stable and meaningful commitment to aid work, that would be pretty great.
Even so, we shouldn't want everyone to do the same thing. One thing that bothers me about these kinds of discussions is that the alleged obligations sometimes seem to be herding everyone into the same restrictive mold -- as though there was only one way for a person to lead a good life. Such a world doesn't sound at all appealing to me. I think a world with artists, clowns, and all the rest, is actually better - more valuable - than one where everyone is working directly to relieve suffering. Partly this is because these other vocations indirectly enrich the lives of many people, and it's hard to estimate the run-on effects of this for creating a happier future. But it's not just instrumental: perfectionist values and "civilization" are arguably the greatest goods we could hope to see advanced in the world -- and this is more important, I think, than merely removing the bad.
So, given that the world I want to live in is one that contains such vocational plurality, ethical holism then implies that it's morally permissible to pursue any one of them. (An individual may fill any role that is part of the best structure. You can't promote a general structure without permitting its specific implementation.) The globally optimal framework will not necessarily demand optimality from each individual who is part of it. So it is enough to fill a needed or desirable role, even if it is not the most important role in the system. Still, not everything is permitted: there may be some roles (producing manipulative advertising springs to mind) that have no place in a good world. But my position is less demanding than some consequentialists would have it.
This fits in with my general view that the most demanding work of morality should be done at the level of politics and institutional structure, leaving individuals with a very broad space of moral autonomy within which they may shape their personal lives. Such freedom is likely the best way to encourage the passionate pursuit of the diverse values we would hope to see realized in the world, and also seems good in its own right.
So I'm not at all sympathetic to claims that people are morally obliged to pursue one or other particular vocation "for the greater good". Such alienating, impersonal motivations cannot sustain us for long, and the best world has room for our diverse passions in any case. It is important that our chosen vocations have a legitimate place in the good world (or play some role in bringing such a world about); but beyond that requirement, the choice is rightly ours.