I would assume that most shops would say since they are paying for their inclusion in the site they shouldn't be open to negative remarks...aka every bad review would be "shop bashing". I'm not saying every review would be, but they sure as hell wouldn't want a bad one out there; then you are left with positive reviews, which is what it is now.

I'm not saying every site sponsor would do that, but undoubtedly some would. That and your can guarantee things will get out of hand almost everyday.