1. A method comprising: registering an initial user of a first communication service with a second communication service; receiving a list of contacts associated with the initial user; identifying, using at least one processor, a user identity contained in the received list of contacts that corresponds to a subsequent user; receiving a request for the initial user to receive a notification when the subsequent user registers with the second communication service; identifying a registration by the subsequent user with the second communication service subsequent to registering the initial user with the second communication service; and in response to identifying the registration of the subsequent user with the second communication service, and based on the request, providing, to the initial user, a notification that the subsequent user has registered with the second communication service.