A practice that underhandedly deposits cookies from merchants onto users computers when the user has never visited the merchant through the affiliate's link and potentially may not have even the affiliate's website. Cookie stuffing is done with the intent of stuffing as many cookies as possible onto as many user computers as possible in the hopes that they eventually come accross the merchant website and make a purchase. The larger and broader the merchant, the more likely that is to occur (think Amazon). Cookie stuffing is heavily looked down upon by legitimate affiliates and most merchants ban affiliates using cookie stuffing in their affiliate agreements.
Once you've protected your prospecting pool, maximize your affiliate program by working with the best and leaving the rest. As the old 80/20 adage implies, most of your revenue will come from a very small percentage of your affiliates. Because it can be time-consuming to manage a larger affiliate network, consider selecting only a few companies initially, and interview them before signing them on. Affiliates are an extension of your sales force and represent your online brand, so choose partners carefully.