In the aftermath of last summer's sudden fad for the victims of Lou Gehrig's Disease, American charities were struck with “Ice Bucket Fever.” People raised $115 million for the ALS Foundation — a charity that took in less than $3 million in August of last year — by dumping ice on their heads. But the exercise in viral giving was not sustainable for humanitarian fundraising. Charities that go viral are not always cost effective. Why do people donate to one thing and not another? Can Social Media help lift the level of giving above the tiny percentage of GDP, where it's languished for years?