Payvment is a facebook application, which offers to shop owners space to host their products for free. Users can browse products based on categories or search based on keywords. This application has approximately 400 000 monthly users.
Useful features for Shopster:
-Two applications in one: one application for owners of stores to advertise items and one application for buyers.
Pros:
-Many users that can help the application to function properly.
-Users can shop directly from inside of facebook.
Negative:
-No location based search supported by this application.
-It is like any other eshop that sells various items, it does not suggest (other) shops.
source: http://www.facebook.com/payvment