That's the walkaway dilemma. If you take without giving, you're a mooch. If you keep track of everyone else's taking and giving, you're a creep scorekeeper. It's our version of Christian guilt--it's impious to feel good about your piety. You have to want to be good, but not feel good about how good you are. The worst thing is to be worrying about what someone else is doing, because that has nothing to do with whether you're doing right.