I heard someone on TV the other day (I can't remember who) say "greed is necessary for success". Part of the reason that I can't remember who said it is that it is so wrong, it wasn't worth remembering.
Greed means that success is measured by maximization. In other words, you are only successful if you can squeeze every last drop out of the stone. Greed means you are always focusing on more and you can't get enough.
This is why we set goals that will indicate our success, not simply try to get "all that we can". When you are greedy, you risk not focusing on people, ethics, or laws. Even worse, you can justify it because you've made the focus "getting more", not "getting enough".