It's not just Amazon its everything. Companies spend large quantities of money on media control, we all know this. I probably a hand full of media companies in the USA, China, and India that are selling a review control service.
It may be that I am getting old and that the culture has changed but I'm not sure...
A second service would be to have Americans pressure a site to have detrimental user content removed. For example, if someone starts a thread about how the name of my product was stolen from an indigenous community's recipe, our service would nip that in the bud.
Your brand management department would love us. These services already exist.