The Giving Pledge is a philanthropic campaign started in June 2010 by American billionaires Warren Buffett and Bill Gates. Its mission is to invite the wealthiest individuals and families in America to commit to giving the majority of their wealth to philanthropy. The pledge is a moral commitment to give not a legal contract. As of August 2010, 40 billionaires in the US have joined this campaign. Click here to see who is committed to this outstanding act of altruism and read their pledge letters to see why altruism is important to them.