I still do not understand how you say selling a share is different to selling the whole plane.
Can anyone clarify this?? If you go to the super super market and by half a melon and the bloke next to you buys a whole melon, both people have a bought melon and the super market has sold melon.
As for Classifieds section, I don't think it is a bad idea but must admit it might well take some policeing. It might be an idea that has a disclaimer stating they are in no way responsible for buyer or seller protection and are not responsible for financial transactions. However charging a commision or fee for the sale post is perfectably understandable.