“The idea that the government of a major advanced country would default on its debt -- that is, tell lenders that it won't repay them all they're owed -- was, until recently, a preposterous proposition. Argentina and Russia have stiffed their creditors, but surely the likes of the United States, Japan or Britain wouldn't. Well, it's still a very, very long shot, but it's no longer entirely unimaginable. Governments of rich countries are borrowing so much that it's conceivable that one day the twin assumptions underlying their burgeoning debt (that lenders will continue to lend and that governments will continue to pay) might collapse. What happens then?” asks Washington Post writer Robert J. Samuelson.