A recent Slate article comments on work in Psychological Science in which people are used for an experiment (the 'people' are probably university students) on moral behaviour and 'buying green'. The subjects are asked 'What do you want to buy from Online Store X' (the experimenters manipulate the store's stocks), which is all good and fits with experimental protocols (oh yes, though it's imaginary, and they aren't spending money, so hey?). What is not cool, not cool at all, is that the experimenters then set up a dictator game telling the players they were paired with someone, when they weren't. The money they were 'giving' to someone else, didn't get given to anyone. The experimenters deceived their subjects. Not cool. Fantastic that they are doing experimental work, and using economicky experiments to do it, but not cool that they deceive their subjects. Why? Experimenter legitimacy! One of the big battles as an experimentalist is having your subjects BELIEVE that what you say you will do, you ACTUALLY will do. If word of this kind of deception (almost always by psychologists) gets out, then more and more experimental subjects won't believe experimenters and therefore won't behave in ways consistent with how they would outside of the laboratory or experiment. This is why economics experimenters have such a strong code of ethics about not deceiving and doing what you say you will do.