Craig Newmark, the founder of Craigslist, has given away half a billion dollars to charity since founding the company 30 years ago. He has signed The Giving Pledge, a philanthropic campaign that encourages the ultra-rich to give away vast sums during their lifetime. Newmark's philanthropy is rooted in his childhood lessons on kindness and treating others with respect. He believes that giving back is important and that others with vast fortunes should consider doing the same.