The fundamental problem is anonymity. People exaggerate, stretch the truth and lie more often if they think no one will know who they are. I know this from "reviews" on Rate My Professor, to speak to my own field of work.
On SCF even though people have screen-names rather than using their "real" names, they are not as anonymous as on Yelp or Rate My Professor or
Amazon reviews. People develop a profile here, after 100 or so posts. Many use their own first name when they conclude a comment.
Moreover, some are tied (by their choice) to their
ebay stores or offerings. To what degree an
ebay seller is linked to a "real" person's profile varies, but if one has bought from an
ebay seller, one learns (in most cases), the mailing address and real name of the person once a shipment arrives.
A few even use their full real names as their screen names here.
SCF members want to be liked and respected, just as most people in general do. So an SCF member is "accountable" to some degree, even under his screen name, for what he writes. This is not true of Yelp and its many variants.
Hence, Yelp reviews are next-to-useless. Worse than that, it has become a form of slander and character-assassination. But people treat these reviews as if they are trustworthy. Same for Rate-my-Professor which has now become a major factor in how students choose which classes to register for, at least at my university.
Yes, it is true that one can read-between-the-lines in an
Amazon or Yelp or RMP review and arrive at some elements of truth. Systems that give an identity to a reviewer over multiple reviews (
Amazon) are closer to what happens here on SCF than those that are totally anonymous--where one has no idea which or how many reviews are coming from Person X or Person Y, like RMP or (I think) Yelp.
So there's a hierarchy, with Yelp and RMP at the bottom. And the key factor is the degree of anonymity. Total anonymity leads to total unaccountability and thus to virtually total non-credibility.