Selecting advertisements for users of a social networking system using collaborative filtering

A non-transitory computer readable storage medium storing one or more programs configured to be executed by a server system, the one or more programs comprising instructions for:

• maintaining an interaction log by a social networking system, the interaction log including information about a plurality of user interactions with a plurality of objects in the social networking system;
• computing a similarity score for each of a plurality of pairs of the plurality of objects, each similarity score based on a measure of users who have interacted with both of the pair of objects, normalized by a number of interactions by the users with one or both of the pair of objects;
• identifying, from the interaction log, an interaction with a first object of the plurality of objects by a viewing user;
• selecting a second object from the plurality of objects based on the similarity score between the first and the second object;
• and
• sending an advertisement associated with the second object for display to the viewing user.

A method comprising:

• maintaining an interaction log by a social networking system, the interaction log including information about a plurality of user interactions with a plurality of objects in the social networking system;
• computing a similarity score between a first object and a second object, the similarity score based on a measure of users who have interacted with both the first object and the second object, normalized by a number of interactions by users with one or both of the first object and the second object.
• identifying, from the interaction log, an interaction with a first object by a viewing user;
• selecting the second object from the plurality of objects based on the similarity score between the first object and the second object;
• and
• sending an advertisement associated with the second object for display to the viewing user.