Abstract: A facility for tracking the sharing of distinguished content is described. When a user seeks to access the distinguished content from a client computer system using a URL associated with the distinguished content, the facility determines whether a user identifier is represented in the URL. If a user identifier is represented in the URL that is different from a user identifier that is persistently stored by the client computer system, the facility determines that the distinguished content has been shared with a user identified by the user identifier that is persistently stored by the client computer system by a user identified by the identifier represented in the URL.

Abstract: A facility for populating an advertising segment is described. For distinguished content, the facility accesses a data structure that, for each of two or more users, relates an instance of sharing of the distinguished content to the user with one or more instances of sharing the distinguished content from the user. The facility accesses a segment definition that specifies a test that, for each of the users, is either satisfied or not satisfied based upon the contents of the data structure. The facility selects the users for whom the test is satisfies, and constructs a list of identifiers identifying the selected users.

Abstract: A facility for tracking the sharing of distinguished content is described. When a user seeks to access the distinguished content from a client computer system using a URL associated with the distinguished content, the facility determines whether a user identifier is represented in the URL. If a user identifier is represented in the URL that is different from a user identifier that is persistently stored by the client computer system, the facility determines that the distinguished content has been shared with a user identified by the user identifier that is persistently stored by the client computer system by a user identified by the identifier represented in the URL.