One of the major issues is the sellers selling a product for a major discount or even free, you get a refund when youve posted a positive review, this is a big no no from amazon, they will come down on the seller, but it still does not stop them from doing it, so you get lots of positive that are not 100% cosher.
Another is, the deals section, a lot of the items are items from sits such as wish.com and lets face it, we all know what their products are like lol
I am a big Amazon fan and use it weekly if not multiple times a week, i like the convenience and customer service should something go wrong, especially if its provided by and shipped by amazon. been a few times where something has gone wrong, for example, just the other day, the Sandisk 64gb U3 for my P4P didnt turn up the next day as per 1 day shipping, they sent a new one, i asked what if the old one turns up, they said keep it and gave me a fiver for the trouble. It did turn up the next day, so being honest, i sent one back and being good to their word, they refunded the original one so i got it free, little things can go a long way....