Spot on. It is actually one of the explanations in the Gneezy and Rustichini paper: "consider the practice of paying back a small amount for recycling a soft drink bottle, which is common in many European countries. Anecdotal evidence suggests that people are less willing to recycle when this small compensation is offered, than they are in places where no money is offered, and failure to recycle is simply considered bad behavior. It is unlikely that the amount offered is considered insulting. A different explanation in this case might be that people are afraid of looking ‘‘cheap’’ for making the effort of recycling to collect the small amount."