Bill Gates shares possibly 'the most important thing' he's learned from Warren Buffett

"Everyone should have a friend as thoughtful and kind as Warren Buffett," Bill Gates said in a recent blog post honoring his friend for his 90th birthday. "Even though he keeps up a hectic schedule ... he picks up the phone and calls to say hello. He regularly sends articles he's read that he thinks Melinda or I will find interesting," according to Gates.