I dunno, I can only speak for myself but I wouldn't hoard the loot just because I was there first. Even if it wasn't a matter of mutual cooperation, it would just seem a bit unfair, really: I know some people can get really competitive, but would any reasonable person really do so to the point of depriving people who they're supposedly cooperating with?
I don't deny I like the allure of "ooh shiny!" but not to the point where I'd consider spiting others. And if I found someone repeatedly doing that to me, I dare say I wouldn't be terribly impressed, nor inclined to continue playing alongside them. I would still assert that reasonable people don't need to be corralled into behaving reasonably.
