Greed

This is an old story and a little humorous:

One day Abraham Lincoln was walking down the street with two small boys who were both crying loudly.
A neighbor passing by inquired, “What’s the matter, Abe? Why all the fuss?”
Lincoln responded, “The trouble with these lads is what’s wrong with the world; one has a nut and the other wants it!”

But it illustrates a big problem and the oldest one known to man -- greed.