System and method for enabling proximity-triggered messaging in certain coverage areas for social networks and communities-based services. The system includes at least one local unit with cellular radio transceiver, located within a corresponding coverage area. The cellular transceiver broadcasts a LAC different from any other LAC of the radio cells in the surroundings; establishes a Location Update dialogue with any mobile phone answering to the LAC broadcast, obtaining its IMSI number; sends a Location Updating Reject message to each mobile phone whose IMSI number has been obtained; and sends said IMSI number to a central unit. The central unit obtains, for each IMSI number, one valid identity in a community-based service; and provides at least one social network server associated to the corresponding valid on-line identity with the valid identity.