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Amazon works well in certain instances, not in others. I've found I can double my income by using AdSense on reviews I wrote for Amazon.
Content sites generate significantly higher ROI, year in, year out, with multiple targeted varying revenue options on every page.
Relying upon only one or two, whether AdSense, Amazon, or whatever, will be a short term rollercoaster - fun, great while it lasts, but always ending too soon.
There are lots of revenue options: pick, choose, and test to determine the best for each niche, each site, each page. None are perfect and all change their Terms and Conditions like women's fashions. Be aware and open to those changes. And work at it. Create your own. Sweat equity on the web returns increased knowledge which can return profits (relatively) forever - certainly long after the work has been done.
Just as one site can get lost in the SERPs, one revenue source can dry up. Multiplicity is as important on the web and in business as in life.