System for and method of generating advertising inventory by marketers sharing content with others

A system of generating advertising inventory by marketers sharing content with others via a social network or other electronic communication across a network. This embodiment may include allowing one or more content providers to provide links to content items. The content items may be provided directly by the content provider or by a clearinghouse entity or other intermediary. A subscriber may then search for relevant content items from one or more content providers. The subscriber may provide ancillary content for association with the selected content item. Thus, when the subscriber shares a URL identifying the selected content item via a social network, the URL may be encoded with a unique identifier identifying the subscriber. When the URL is clicked by a user, an ad server on the publisher's side may recognize the unique identifier and display the content item with the ancillary content provided by the subscriber.