And it being a "social" thing, there's nothing stopping you from reaching out and having a conversation with reviewers.
Still, I would at least like to see something like what I mentioned tried.
I have some ideas on ways to tackle the fraud problem, such as with a trust-based ranking system, rewarding balanced feedback, purchase verification, looking for heuristics of fake reviews, and avoiding potential conflicts of interest.
It's not the primary concern of Amazon to make sure their reviews are authentic, where as it would be with a service dedicated to that very concern. In fact, positive reviews help drive more sales, so there's an inherent conflict of interest that I feel justifies the need to separate reviews from the place selling the things being reviewed.