It's easy to review entities that all exist in a single database.Consumer electronics products are far harder to find categorized in a single place.You also have to contend with the fact that movies are essentially immutable - if you watch the same edition as someone else you are seeing an identical product. Consumer products might be damaged, might be counterfeit, or might be incorrectly classified. All of these makes it really hard to build a single source of truth for reviews.The bigger issue...