1. A method comprising, by a client device of a first user associated with a first node in a social graph: accessing a tag that encodes information regarding a second node in the social graph, the second node being associated with a second user or a concept; determining based at least in part on the tag a social action to take on the social graph with respect to the first and second nodes; and transmitting, to one or more computer systems of a social-networking system maintaining at least a portion of the social graph, a message configured to effect the social action on the social graph with respect to the first and second nodes.