Dependency: This is the biggest con, so pay attention! Affiliate marketers depend on the merchant to make their money. If there were no merchants or affiliate programs, the possibility of being an affiliate marketer would not exist. It even becomes more frustrating if for one reason or the other a merchant suddenly stops running the business or their affiliate program. This can potentially deprive the affiliate marketer of his one-time steady source of income.
If you try to sell a product that is in low demand then chances are that you are not going to get many sales no matter how hard you try. So it is a good idea to spend a bit of time researching and finding out if a product that you are thinking of promoting is a product that your audience needs. If your site gets decent traffic then you can conduct an online survey and easily get input from your visitors.

For example, if I talk about how cool a product is, and then you find out that I’m an affiliate for them, wouldn’t you as a conscientious observer become skeptical as to whether my information is biased, if perhaps I’m only saying how cool something is because I can get paid for it? Wouldn’t that make you question my integrity with other things I say as well?