A method includes storing interaction data related to a first user and at least one other user. The interaction data is indicative of interactions among mobile devices operated by the users. The method further includes generating respective ranking data for each of the other users besides the first user. The ranking data is derived from the interaction data pursuant to at least one ranking rule. In addition, the method includes storing transaction data for the other users. The transaction data indicates product purchases made by the other users. An offer or product recommendation is selected based at least in part on the ranking data and the transaction data. The offer or product recommendation is transmitted to the first user.