Affiliate marketing is a touchy subject. Very few people see the problems lurking behind the promises of riches and freebies, and those who do would often rather ignore them - after all, it’s rewarding for them to defend the concept. In reality, affiliate marketing is a very problematic concept, deeply unethical, and a threat to a healthy market (insofar that is possible). This is why.
Affiliate marketing turns every customer into a salesman
I’ll start out with an analogy to illustrate the problem.
Imagine that you walk into an electronics store, and you need a new phone. The moment you walk in, the head of every other customer in the store turns... and a few seconds later they’re all running towards you, holding phones, and trying to convince you to buy one from them rather than from any of the other guys.
No matter what question you ask them, you’re not getting a useful answer - most of them have no idea what the answer is, and the rest seems to lie about it.
You flee from the store, walk into a different electronics store... and the exact same happens. Three hours later, you go home tired, without a phone, simply because you couldn’t figure out what you needed.
This analogy might sound insane, and that's because it is - but it’s the exact thing that happens with affiliate marketing on the internet. The line between “salesman” and “customer” becomes blurred, leading to a barrage of attempts to sell you things, and very little useful information. Often the people trying to sell you things, don’t even really know what they’re selling you.
Affiliate marketing invites deception
In affiliate marketing, nobody has a genuine edge. Everybody is selling the same product, and the only way to differentiate yourself is through the method you use to sell it. This very quickly leads to dishonest behaviour - after all, how else are you going to sell something that isn’t part of the product itself? All the affiliate link spamming, false claims, and embellishments are a direct result of this situation.
Affiliate marketers have to resort to such tactics in their line of business - they wouldn’t have a business otherwise.
Affiliate marketing defeats the natural model of peer reviews
In a normal market, you would often rely on the opinions of your peers, to determine whether something is worth buying. But what if your peers have become (affiliate) salesmen, who need to use deception to have a business?
Affiliate marketing creates a “trust nobody” environment. The moment an affiliate link or code is involved, you cannot tell with any certainty whether their “review” or “opinion” is genuine, or just a manufactured marketing ploy. When a market relies heavily on affiliate marketing (such as, for example, the shared web hosting market), this makes it virtually impossible to find objective information about the quality of different products or services.
I’m sure you’ve run across one of the myriad “top shared webhosting” lists, that pretend to contain reviews, but actually are nothing more than a shoddy marketing ploy - and that is only a single example of them.
In its core, affiliate marketing is all about making subjective data look objective - and gaining some personal profit from it in the process. And that is what makes it unethical.