1. A computer-implemented method comprising: accessing, at a computer system, data that is associated with a social network; determining social relationships among members of a group of computer users based on the data that is associated with the social network; generating a social graph comprising a plurality of nodes and a plurality of edges, wherein each of the nodes represents a member of the group of computer users, and each of the edges connects two or more of the nodes, i) represents a social relationship between two or more of the members that are represented by the connected nodes, and ii) describes a type of acquaintance relationship between the two or more of the members that are represented by the connected nodes, wherein at least some of the types of acquaintance relationships in the social graph are automatically determined by the computer system using data that represents historical instances of electronic correspondence between two or more members of the group of computer users, at least some of the electronic correspondences occurring outside of the social network; receiving, at the computer system and from a first computing device that is associated with a first user who is a member of the group of computer users, a request to distribute content to other members of the group of computer users, wherein the request specifies the content to be distributed; receiving from the first computing device, an indication that the first user of the first computing device has selected, from among multiple provided types of acquaintances, a particular specified type of acquaintance with which the content is to be distributed, wherein the first user has, with one or more computer users of the group of computer users, acquaintance relationships of types different than the particular specified type of acquaintance; identifying, from among the group of computer users and using the social graph, one or more second users who have one or more acquaintance relationships, of the specified type, with the first user, wherein at least some of the types of acquaintance relationships in the social graph are automatically determined by the computer system using data that represents historical instances of electronic correspondence between two or more members of the group of computer users, at least some of the electronic correspondences occurring outside of the social network; receiving, at a later second time, an indication that a computing device has requested an electronic document that includes: (i) document content that is displayed as part of the electronic document and (ii) a reserved area for user-submitted content; based on a determination of whether the computing device corresponds to one of the one or more second users, either transmitting default content to the computing device for display in the reserved area of the electronic document, or determining whether to distribute the content submitted by the first user to the computing device for presentation in the reserved area of the electronic document, wherein the determination of whether to distribute the content to the computing device is based on (i) whether the one of the second users has at least an acquaintance relationship of the specified type with the first user, and (ii) whether the content submitted by the first user pertains to one or more topics of the document content; and based on the determination of whether to distribute the content submitted by the first user with the electronic document, transmitting the content submitted by the first user to the one of the second users for display in the reserved area of the electronic document.
1. A computer-implemented method comprising: accessing, at a computer system, data that is associated with a social network; determining social relationships among members of a group of computer users based on the data that is associated with the social network; generating a social graph comprising a plurality of nodes and a plurality of edges, wherein each of the nodes represents a member of the group of computer users, and each of the edges connects two or more of the nodes, i) represents a social relationship between two or more of the members that are represented by the connected nodes, and ii) describes a type of acquaintance relationship between the two or more of the members that are represented by the connected nodes, wherein at least some of the types of acquaintance relationships in the social graph are automatically determined by the computer system using data that represents historical instances of electronic correspondence between two or more members of the group of computer users, at least some of the electronic correspondences occurring outside of the social network; receiving, at the computer system and from a first computing device that is associated with a first user who is a member of the group of computer users, a request to distribute content to other members of the group of computer users, wherein the request specifies the content to be distributed; receiving from the first computing device, an indication that the first user of the first computing device has selected, from among multiple provided types of acquaintances, a particular specified type of acquaintance with which the content is to be distributed, wherein the first user has, with one or more computer users of the group of computer users, acquaintance relationships of types different than the particular specified type of acquaintance; identifying, from among the group of computer users and using the social graph, one or more second users who have one or more acquaintance relationships, of the specified type, with the first user, wherein at least some of the types of acquaintance relationships in the social graph are automatically determined by the computer system using data that represents historical instances of electronic correspondence between two or more members of the group of computer users, at least some of the electronic correspondences occurring outside of the social network; receiving, at a later second time, an indication that a computing device has requested an electronic document that includes: (i) document content that is displayed as part of the electronic document and (ii) a reserved area for user-submitted content; based on a determination of whether the computing device corresponds to one of the one or more second users, either transmitting default content to the computing device for display in the reserved area of the electronic document, or determining whether to distribute the content submitted by the first user to the computing device for presentation in the reserved area of the electronic document, wherein the determination of whether to distribute the content to the computing device is based on (i) whether the one of the second users has at least an acquaintance relationship of the specified type with the first user, and (ii) whether the content submitted by the first user pertains to one or more topics of the document content; and based on the determination of whether to distribute the content submitted by the first user with the electronic document, transmitting the content submitted by the first user to the one of the second users for display in the reserved area of the electronic document. 13. The method of claim 1 , wherein the content comprises a link to the first user's profile on the social network.