Philanthropy has a special buzz among the ultra-rich. If net worth matters, so does how much is given away. But who to give to and for what? Should it be an instinctive decision or a calibrated one?

These are vexing concerns. Entire teams in large foundations work on vetting proposals, checking out NGOs and then holding them to account. But then there are also big donors who believe it makes practical sense to cut a cheque and forget about it.