Since the emergence of affiliate marketing, there has been little control over affiliate activity. Unscrupulous affiliates have used spam, false advertising, forced clicks (to get tracking cookies set on users' computers), adware, and other methods to drive traffic to their sponsors. Although many affiliate programs have terms of service that contain rules against spam, this marketing method has historically proven to attract abuse from spammers.
Another difference is that with affiliate marketing business, an affiliate can sell different products all at the same time. His selling potential is limitless. Even if the products are not related to one another, he can still do affiliate marketing. He only needs to create a separate website to market different products. Unlike with offline middleman marketing, a middleman must only sell related products to maintain his credibility, for who would take a salesman seriously who sells cars and baby products at the same time?