1. A method comprising: receiving an update to a user profile that describes a user and indicates a group of users socially connected to the user by a social network, the update referencing a community of the user and being received from a device of the user; modifying the user profile based on the update by including a reference to the community of the user within the user profile; identifying a further user that is included in the community and that is socially unconnected to the user by the social network, the identifying of the further user being performed by a processor of a machine based on the update that references the community of the user; and providing a notification that the further user is included in the community, the notification being provided to the device of the user.