7. An apparatus comprising: a memory to store: one or both of a first entity and a datum associated with the first entity, and one or both of a second entity and a datum associated with the second entity; and a processor, operatively coupled to the memory, to: determine a plurality of subjective attributes for a first entity based on terms from a plurality of user reactions to the first entity, wherein the terms are not a user-supplied tag; determine respective relevancy scores for the plurality of subjective attributes with respect to the first entity using at least a number of occurrences of a plurality of users bookmarking the first entity; obtain a first set of features for the first entity; and train a classifier on a set of input-output mappings, wherein the set of input-output mappings comprises an input-output mapping whose input is based on the first set of features and whose output is based on the respective relevancy scores for the plurality of subjective attributes with respect to the first entity, wherein the trained classifier is to be applied to a second set of features of a second entity to obtain respective relevancy scores for one or more subjective attributes with respect to the second entity.
7. An apparatus comprising: a memory to store: one or both of a first entity and a datum associated with the first entity, and one or both of a second entity and a datum associated with the second entity; and a processor, operatively coupled to the memory, to: determine a plurality of subjective attributes for a first entity based on terms from a plurality of user reactions to the first entity, wherein the terms are not a user-supplied tag; determine respective relevancy scores for the plurality of subjective attributes with respect to the first entity using at least a number of occurrences of a plurality of users bookmarking the first entity; obtain a first set of features for the first entity; and train a classifier on a set of input-output mappings, wherein the set of input-output mappings comprises an input-output mapping whose input is based on the first set of features and whose output is based on the respective relevancy scores for the plurality of subjective attributes with respect to the first entity, wherein the trained classifier is to be applied to a second set of features of a second entity to obtain respective relevancy scores for one or more subjective attributes with respect to the second entity. 8. The apparatus of claim 7 wherein the determining is further based on a plurality of users adding the first entity to respective playlists.