I have heard it said that it is immoral to be a billionaire.
Think about it. If you are worth, say, $500 million, what can you possibly want or need that requires you to gather another $500 million?
It's possible to have some big projects in mind, and gather money to spend on making them happen, but surely those projects should be intended to benefit large numbers of people. The Clinton Foundation rebuilt the healthcare system of an entire country, that's the kind of thing I have in mind. The Gates foundation has done good work too, but Bill needs to step it up. He could do more.
The only person I know of that was once a billionaire and now isn't, because she gave away so much money, is J. K. Rowling.
<edit>
Lifted from Facebook.
Sadio Mane, a Senegalese soccer star. earns approximately $10.2 million annually, has given the world a rude awakening after some fans spotted him carrying a cracked iPhone. His response is legendary:
"Why would I want ten Ferraris, 20 diamond watches and two jet planes? I starved, I worked in the fields, played barefoot, and I didn't go to school. Now I can help people. I prefer to build schools and give poor people food or clothing. I have built schools and a stadium; provide clothes, shoes, and food for people in extreme poverty. In addition, I give 70 euros per month to all people from a very poor Senegalese region in order to contribute to their family economy. I do not need to display luxury cars, luxury homes, trips, and even planes. I prefer that my people receive some of what life has given me."