This passage epitomizes the poverty of utilitarian thinking (and philosophy in general) - it takes conventional notions as understood by the philosopher and raises them to the level of absolute truths , supposedly valid for every human being ever. This is no much different from a local yokel saying that all foreigners are x because the one he met is x. I cannot believe that intelligent people seriously debate this crap.
A more enlightened approach is to investigae how "prizes" are defined by different people and what accounts for the differences. For example, for Native Americans in the Northwest, the "prize" was not to hoard stuff for oneself, but to give away as much as possible (cf. potlach). The tradition of potlach was so anti-thetical to capitalist ideology that it was banned by the Canadian gov't until i970s. Yet, it would be a gross mistake to view it as an expression of exceptional altruism.
Potlach was simply a tradition of buying social prestige by chieftains and that served a very utlitarian function - attracting new people to a particular tribe or a village. Human resources were always th emosty valuable assets among Native Americans, and they took great pains to maximize them, or at least keep them from dwindling.
The sociologist Joseph Galaskiewicz found that philanthropic giving among US business elites serves the exact same purpose - buying social prestige and access to elite circles to enhance one's social capital.
In the same vein, the answer to Doug's argument that utilitarianism is about "voluntary" social intercourse is: "voluntary" can mean different things by different people in different situation. To continue our Native American example - Natives sometimes kidnapped whites, especially women, which led the pundits of that time to tell horror stories about 'Indian savagery.' Of course, the idea of 'savagery' was based on the notion of 'deprivation of voluntarism' that such actions involved. What the stories did not tell was that kidnapping was another act of maximizing human resources by the Natives - specifically, by replacing the missed or deceased members of the tribe.
The kidnapped women typically gained a status equal to other tribe members, which in relative terms was much higher than their status among the 'freedom loving' christians. Consequently, there are documented cases of those kidnapped womend refusing to go back to christian society when they had a chance to do so. in some cases, they had to be forced back.
So "voluntary' in that context means anything one wants it to mean, that is, nothing in particular. In my vocabulary, "voluntary" is a concoction of bourgeois ideology to legitimate bourgeois property relations and means "acquired throught a nominal consent of others, as defined by conventional rules of doing business, hence legitimate." Aside that, the term has no empirical meaning.
So the bottom line is that a scientifically correct approach is to look at a larger context of a particular behavior and analytically separate effects of different environmental factors, subjective defintions of situations, etc. However, the utilitarian philosophers (may their books burn in hell) are seemingly incapable of such rudimentary analytic procedures. Instead, their arguments rest on concocted fairly tales (aka "games') devoid of any empirical context.
Paraphrasing Jesse Ventura: utilitarianism is an intellectual sham and a crutch for weak-minded people.
wojtek