Greed is just part of human nature....
I think that the statement "greed is part of human nature" is one of the biggest cop-outs on the planet. I think that humans are a social mammal and, as such, have the desire to gain social influence. We happen to be living in a culture that values the accumulation of material wealth as a signifier of status. Status, to a large degree, confers influence. While greed is a consequence of instinct, it is not itself an instinct. Any takers?
I edited this post to refine my argument as per DuB's suggestions. Furthermore, I should make it clear that the context for this statement being a cop-out is arguments about social organization and that I am not including the desire for non-coercive influence in the definition of greed as that is not pertinent to the context.