I agree with your assessment and that's basically where I'm at with the idea. There's absolutely _something_ there, but gaining traction is going to require _significant_ effort (money?).
Re: talking to users first - 100%! I am fairly active in my community and talk with local business owners all the time. This is where I got the idea in the first place ;). Agreed though that doing this formally and generating some user stories before any development could help focus MVP.
Negative review is definitely a big problem and I'm not an expert on that topic, at all ;). If such an app were to have a review system it would be imperative to ensure the trust-worthiness of reviews shown to users.
Though, I'm not sure you would need reviews at first, at all. I generally trust most of what I buy from a given shop X... I trust their purchasing and supply chain departments to have done the research for me. I never think twice about buying X electronic from Target, for example, wondering if that night light for my son's room is going to combust. One of the benefits of brick and mortar, I suppose.