Its amazing that someone would "add up" future "unfunded liabilities" over an "infinite horizon" and then make the statement that the US owes $100 Trillion. Using the same logic I will probably spend at least a million dollars over my lifetime so someone could say I am in debt right now for a million...makes about as much sense. The gov't can make changes to entitlement programs at any time which would radically change the assumptions about these future liabilities.