Jonathan Stark set up a website to promote a social experiment based on take a penny give a penny that happens in America. This is the type of social experience that we can all like. Unfortunately there will always be some who take advantage and try to take advantage of others.
Here are two members of staff in my local (to work) StarBucks coffee shop in The UK (birmingham) who were pleasantly surprised that this experiment would take place at all.
check out http://jonathanstark.com/card/