Hey Steve,
That's a great question and I am actually pretty surprised more people have not replied.
Anyway, I don't do much Amazon promotion now a days but I used to do it quite often and the only products I would ever promote were products I either purchased myself or had access to (via friends, family, etc.).
I was actually quite successful and I strongly believe that was because I would provide honest reviews and would include videos or photos whenever possible. This let my readers, subscribers, etc., know with 100% certainty that I did actually own and/or use the product and I wasn't just trying to sell them something that I had no first hand knowledge of.