Spam is the biggest threat to organic search engines, whose goal is to provide quality search results for keywords or phrases entered by their users. Google's PageRank algorithm update ("BigDaddy") in February 2006—the final stage of Google's major update ("Jagger") that began in mid-summer 2005—specifically targeted spamdexing with great success. This update thus enabled Google to remove a large amount of mostly computer-generated duplicate content from its index.
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?