Think of the food court at the mall. Most of the time, mallsters will go there looking for food in general, then decide what to eat after they’ve checked out the selection. The eaters benefit because they don’t have to wander all over the mall looking for lunch, and the feeders benefit from the added exposure. A referral network works in the same way. The web is perfect for this kind of marketing, since sites with similar audiences can be grouped just by linking them together. Amazon.com has an incredibly successful network of thousands of mini-bookstores. The small bookstores get more customers, and Amazon gets money for the books they sell to the little guys – a perfect symbiotic relationship.