At only 26, Mark Zuckerberg is one of the world’s youngest billionaires, but he’s not keeping it all for himself. By signing onto Bill Gates’ and Warren Buffet’s initiative called the “Giving Pledge,” Zuckerberg agreed to give most of his wealth to charity. “People wait until late in their career to give back. But why wait when there is so much to be done? With a generation of younger folks who have thrived on the success of their companies, there is a big opportunity for many of us to give back earlier in our lifetime and see the impact of our philanthropic efforts,” he said.