As far as I am concern I am shopping online since last 7 years . I have seen the services of amazon awesome and they return the product if you dont like promptly they do what they say not like shopclues and flipkart . everyday there is a new deal and actually they are giving discount on the best products(branded) . they have turn flipkart as flopkart you can see lenovo have given the exclusive rights of k4 note to amazon leaving flipkart xiaomi also left flipkart and tied up with snapdeal .
amazon gives you the original product and as a seller if you are selling something branded they ask you the letter of authentication from the brand itself which gives you a trust that the thing you are buying is original not a cheap copy
moreover you can read the peoples review on the website itself