Companies want their site to be looked at by as many people as possible. Referral schemes (such as this one) get more and more people visiting the companies website.
Companies rightly presume that if more people that pass through their website, more people will invest in a product (although you do not have to).
Therefore these companies (eg LOVEfilm, AOL, The Post Office, Coral Bookmakers) pay large sums of money to referral companies as they will ensure people visit their website.
This money is spent on gadgets for you! (Games consoles, HDTV's and Apple products)
CLICK HERE to watch a BBC news clip on how it works