Any person making money has received it as a return on their provision for the means, they can make all of the money they like and are under no obligation to do anything in particular with it. A moral principle is an absolute, so if you set the moral principle that a person ought to do amazing humanitarian things and sacrifice their self interests for the interests of others, than you have already become a hypocrite. The only reason you'll call on the rich to do it is because they have a greater capacity to do so, but there are many self interests that you have and things you could be doing for others at your own expense on a daily basis. However, we don't, and why don't we? Is it because we are so immoral and that is such a moral act?
No, it's the exact opposite. A moral principle like that is not sustainable pragmatically, or morally. That's why things like socialism fail. The problem is, as soon as you have set the moral principle that one ought to sacrifice their own interests for others or towards a collective, than you have already invalidated the concept of self-interest, and so the people who think along these lines will ultimately work towards such ends which will produce the same flaw, even in those they think they are helping.
It's best to try to help others, while not doing it at unreasonable expense. If I were rich, there were a number of things I would do, but I would not do something that would require me to sacrifice my interests. I would go to places that are impoverished not because of oppressive government but because a lack of motivation to spend, and make large capital investments to increase the quality of life. Perhaps convince a number of corporations to do the same and invest in one area simultaneously so that wealth can be generated instantly. The corporations make money, and so do the workers. In systems that are not so oppressed with taxes on the rich, then motivation for capital investment will cause the poor to get richer as the rich get richer.
We simply need to stop the lines of thinking that the rich have some kind of obligation to do anything with the wealth they've earned.
I think people, even those who wish to give much to others, sometimes don't consider the ethics of how they are making their money. If you wish to help others, isn't it equally important how you earn that money? For instance, that you aren't invested in mutual funds that, depending on your personal beliefs, may include tobacco companies and companies (like G.E.) that produce arms? Or what about some of the jobs we do? We have to eat and have a roof over our heads, but have you ever found yourself working for a company that you have trouble believing in?
What's wrong with producing tobacco or arms?