Mark Zuckerberg, the 31-year-old co-founder, chairman and CEO of Facebook, recently announced that he and his wife plan to donate 99% of their wealth - approximately $45 billion - to charity. On today's Please Explain, Michael Hobbes, a freelance writer who also works for a human rights NGO, talks about how philanthropy is changing, from the Rockefeller and Carnegie foundations, to Bill Gates and Mark Zuckerberg's altruism. 

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