If you build the scheme into you commerce enabled website, then you can use it as a magnet to get others to sell for you. On the www.flybox.co.uk site we have such a scheme and it enables us to sell directly of the magazine advert, providing specific discount promotions. It enables us to have different prices in different countries; and it enables us to track commission payments to third party supporters.
It would be silly to build an e-commerce site without considering this facility.