This is a great question. Let me start off with an example from Beowulf and then give you an example from some other literature.
First, Beowulf for all his positive points, such as his courage, is a proud man. He wants glory for himself. This idea of getting glory for himself can be seen a greed, greed of respect and acknowledgement from others. This might seem like a little thing, but what if there was another hero like him. There would be rivalry and potentially war. This is exactly what happened in the Roman world, which brings me to my second point
Second, the best place to go in the ancient world to look at the topic of greed is Sallust. He is a great writer and his whole point is that the Republic fell, because of greed and ambition. People wanted more and more and this eventually destroyed their society.
Finally, if we focus on Sallust a little more, then the parallels are unmistakable with today's culture. Greed is killing America. Gordon Gecko from the movie Wall Street said, "Greed is good." These words have defined a generation in America and now we are paying for it.
Follow-up question? However, can our society exist and grow without a certain element of greed? Look at someone like Bill Gates. Many people automatically consider him greedy for the vast wealth he has accumulated. But in the process he grew a huge company that has employed many people, he has also developed products that our society wanted and needed to further develop, and through his foundation he donates millions of dollars to charity.
Also, in the novel The Great Gatsby, Gatsby was also considered greedy. Far different from Bill Gates, he accumulated his wealth based on his desire to win the heart of Daisy. His greed was founded on envy, but woudl we really consider his to be selfish or evil?
Arent the majority of humans to some degree greedy? Is it somewhat of a natural characteristic founded on instincts of survival? Is it really more a question of how far one goes with their greed relative to breaking society's rules?