Well, okay, let's see...
My Amazon Affiliate account has been cancelled TWICE because I used "Kindle ebooks" in a Google AD keywords. So, there's that.
Other affiliates I tried have been pointless. For example Taboola, is good for ADs in non-US markets but it paid poorly on the affiliate side.
Lately, for about six weeks, I have been avoiding 'Zon and narrowly focusing on marketing a couple of items. My site traffic has improved but not enough to warrant the trouble of another try at affiliate marketing.
Finally, organic "sales" through D2D and Smashwords have ticked up. I pushed the first book of a series into permafree. A five day run of ADs using keyword "Free" definitely improved my site's indexing. Without any ADs or efforts, I am seeing consistent downloads across platforms and the hits to my site are coming from several new search engines. Heck, Yahoo, which I never use, is driving traffic to my site.
Summary, my take, which is an educated opinion, is: If a site is not pulling 10k+ unique daily visits, affiliate marketing is hardly worth the trouble.
R.C.