If i'm a billionaire why would I advertise bitcoins? Not because Bill Gates is afraid to take risks. Actually he earned that much money and respect by takinga risk. He will not be in his place without taking risk. Maybe he's not into bitcoin because it may be a hinder to his works or in where he is expert. Bitcoin may be a threat for him in a way that if someone becomes a millionaire or billionaire because of bitcoin, it can destroy Bill Gate's popularity. But don't blame hin. He got his own way to be a billionaire and I admire it. Hardworks will be paid off always.