Also what they'll do is the product listing switcheroo, where they'll sell some commodity item that's not necessarily crap and get a ton of positive reviews generated for it, legitimate or otherwise. Then the seller will update the product listing to refer to a completely different item, but all the reviews from the old product are remain attached to it.

A lot of online retailers also filter out negative reviews for things. Sometimes this is because they're shyster bastards, but sometimes it's because the manufacturer(s) of said items bully them into doing it. Two I have personal experience with are Cyclegear/Revzilla, and Rocky Mountan ATVMC. Both of these retailers will refuse to publish negative or middling reviews for their private label "bands" in order to make themselves look better. That's Tusk for Rocky Mountain, and Bilt/Sedici for Cyclegear/Revzilla.