In one embodiment, a method includes sending a request for a measure of affinity associated with a first user for a particular content associated with a second user, where the measure of affinity predicts a level of interest the first user has for the particular content; sending weighting information for computing the measure of affinity, where the weighting information includes information specifying a first weight to be attributed to a first predictor function that is based on the second user and a second weight to be attributed to a second predictor function that is based on concepts associated with the particular content; receiving the measure of affinity; and sending, to the first user, the particular content, based on the received measure of affinity.