Diving into one I think is detrimental to both sellers and customers, Ads. If you are not a huge brand this is a ~mandatory additional cost on top of FBA (or you won't show in results). As a customer it sucks because many of the top results are trash. Why bother having a decent product if you can just buy a ranking and some fake reviews? Amazon is pushing this so hard right now as it is a quickly growing revenue stream for them :(