Depending on how you plan to implement and display the user ratings, I see some potential in this. Say I was browsing store shelves and was interested enough in a product but needed a nudge in either direction, a quick scan and send is easier than mobile googling and can provide me with near instant, useful feedback.

The hardest part as always will be adoption. This will only be useful to me if there is a critical mass of users to supply me with feedback and make me want to leave my own. Figure that out (incentives? Coupons? Humor? Maybe add a lowest local price search function?) and maybe you'll be on to something.