16. The apparatus of claim 14 , wherein each person's corresponding feature vector further comprises: an industry feature correlating a first industry in which the person works with a second industry that is a topic of the electronic content item; and a set of social features derived from social connections of the person.
16. The apparatus of claim 14 , wherein each person's corresponding feature vector further comprises: an industry feature correlating a first industry in which the person works with a second industry that is a topic of the electronic content item; and a set of social features derived from social connections of the person. 17. The apparatus of claim 16 , wherein the set of social features comprises: a first number of other persons in the multiple people for whom at least one affiliation is referenced in the electronic content item; a second number of other persons in the multiple people for whom a number of affiliations referenced in the electronic content item is greater than or equal to a number of affiliations of the person referenced in the electronic content item.