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 .