persistent login

one compromise that amazon does that i think is graceful. lets say you shop at amazon and put some stuff in the cart, but do not complete the purchase
then you come back two weeks later on the same computer and web browser. Amazon does not ask you to immediately log-in again - they read your cookie - and let you continue with your shopping session. BUT when it comes time to actually place the order - possibly with a credit card that is already on file with them - you have to log in (again).