Ebay like features are difficult in a privacy perspective as you have to share your physical recival adress.
But it had me thinking. Have anyone ever tested some service where a middleman handler does the C->B sending?
In a A->B setup you need to share your adress with every single buyer/sender.
But in an A->C->B setup, you could possibly limit your adress sharing with a trusted party C and let C do the routing.