He co-founded Skype. Now he's spending his fortune on stopping dangerous AI.

If you've ever used Skype or shared files on Kazaa back in the early '00s, you've encountered the work of Jaan Tallinn. And if humans wind up creating machines that surpass our own intelligence, and we live to tell about it -- we might have Tallinn's philanthropy, in small part, to thank. Tallinn, whose innovations earned him tens of millions of dollars, was one of the first donors to take seriously arguments that advanced artificial intelligence poses a threat to human existence. He has come to believe we might be entering the first era in human history where we are not the dominant force on the planet, and that as we hand off our future to advanced AI, we should be damned sure its morality is aligned with our own. He has donated more than $600,000 to the Machine Intelligence Research Institute, a prominent organization working on "AI alignment" (that is, aligning the interests of an AI with the interests of human society) and more than $310,000 to the Future of Humanity Institute at Oxford, which works on similar subjects.