Someone on twitter issued a dare to all who could give him "the first name of each of your four great-grandparents." Basic arithmetic there and an identity-theft problem. You, whoever you are, surely have eight great grandparents. It is possible that some of you know the first names of all of them. But the only people who really care for a list of such names are people who are trying to build enough of a profile of you to steal your identity. So, some free advice: even if you do happen to know the answer to the question, and even if it is asked in an arithmetically accurate way: don't answer. Thank you.