For example, when someone buys green, or votes Obama (or Ron Paul or George Bush), whether they do it for themselves or for others. If they feel that they've made some sacrifice in taking the action - then they're likely to feel that something is owed to them. This could be social recognition, the license to get away with something questionable .. whatever it is.
If on the other hand they do it for themselves - "I vote Obama cuz I want healthcare" or "I bought this green bag cuz it serves me better / lets me dump it anywhere knowing that it'll just disintegrate after a few weeks... " whatever it may be - then they're less likely want something more to make up for the "sacrifice".
If I'm right, then we should try to make our customers feel as if they've won whenever they buy / interact with us ;-). "You clicked on THAT button! AWESOM!!!!E!" =)