@orathic:
"Greed may in fact be one aspect of human nature, but greed can lead to civil war, for example."
Well, like any good thing, greed is only good in moderation...too much greed and, yes, you have a problem.
That being said, I'm not throwing in with this crowd's "Greed is bad all the time ever in any circumstance...how DARE you keep your money and not spread it around to every last corner of the Earth!" philosophy.
My personal view of self-interest and money comes from Locke's Apple Tree example, which I'm very fond of:
Suppose you have an apple tree.
You've worked hard to plant and tend to it, and you pick the apples yourself.
Now, you have a pretty damn abundant tree.
You ahve a lot of apples.
So many, in fact, that even after you put some in storage for years to come, you have plenty.
IF these excess apples will spoil before you eat them, THAT may be called waste.
Waste is bad.
You also have very hungry neighbors.
Hungry neighbors--for more than one reason--are bad.
Thus, the logical and moral thing for you to do is to give/sell your excess apples.
HOWEVER, that massive store of apples you have that you WILL eat...you earned them, so there is absolutely 0 shame in "greedily" keeping them all for yourself if you so wish.
Greed/self-interest's good, up until the point where things "spoil," and then you take your excess and use it to create a surplus of happiness and help others with those extra-extra resources, while you keep your resources and save your extra resources in case of an emergency.
One more thing I feel I should note:
Self-interest *can* and, in my view, *does mean your interest in others, including family and friends.*
It is very much in your elf-interest to see your family and friends fed...
So if you feed your family and friends with your excess apples, and the family down the street still starves...
That's sad, but I wouldn't call it your fault or call you a miserable miser of a bastard, after all, you used all your apples up, nothing was wasted; that being said, if you offered them an apple or two, that's great, too, but I'm just saying, as long as the apples/money doesn't go to "waste," you shouldn't have to feel guilty about your surplus, YOU WORKED FOR IT.