Most people give away at least some of their hard-earned cash.
Maybe they drop a few coins in the red kettles at Christmas, write a check now and then to the local food bank or the school fundraiser or throw some cash into the Sunday collection basket.
Berkeley's Mike Hannigan gives most of his money away.
It started in 1991. He had about $20,000 in his bank account and thought about all the good it could do in the world. But he decided not to give it away. Instead, he...