In 2010, Warren Buffett and Bill Gates launched a disarmingly simple campaign they called the Giving Pledge : a public commitment, open to the world’s wealthiest people, to give away more than half their fortune during their lifetime or upon their death. The moment seemed to call for it. Tech was minting billionaires faster than any industry in history, and the question of how those fortunes would impact society was just beginning to take shape. “We’re talking trillions over time,” Buffett told