I love Amazon because of the product reviews. Even when Slashdot was promoting the Amazon boycott over the 1-click patent, i mentioned (can't find my comment, /. seems to stop comment history in 2007 :( ) that B&N was terrible in that they only have positive comments on their website. A negative comment i left on B&N was deleted shortly thereafter. Amazon, however, keeps even the bad reviews.
Here's a couple that caught my attention recently. While looking for a bath overflow cover, this comment has a better idea. This product does indeed grow mold, look at the customer images on the left side of the main picture.
I was looking at comments on using a Kindle in the tub, where it was mentioned (seems to be a common idea) to put it in a ziplock bag to protect it from the moisture (which gets into the debate whether the buttons or swipe is better to turn pages).
I learn a lot from Amazon comments, the 1-stars often tell you what people are complaining about, and the 5-stars many times counter the complaints and have useful comparisons. The 2s, 3s, and 4s, similarly are helpful. I think Amazon's comments are what make Amazon such a great retailer. Well, not the only thing, but, even if i purchase something elsewhere i will go to trusty Amazon to find out the real deal.