This will be a search engine that is paid for advertising in products instead of money. It might need to collect delivery contracts to estimate the values of different advertisements or it could get price information off of the net. Sellers can skip out on monetary losses here by giving products that they already have. For example, if a seller's product is worth $100 after exposure but right now it's worth $50, they can give us product which they have plenty of until those goods are bought at $100. This can also be an advantage among less numerical societies.