1. A method, in a data processing system, for content delivery, the method comprising: identifying a candidate user of a social networking service, wherein the candidate user has an associated profile including a plurality of user-stated concepts of interest; determining a probability that the candidate user is interested in an item of content based on a semantic similarity of the plurality of user-stated concepts of interest and a plurality of concept tags associated with the item of content using a weighted semantic graph, wherein the weighted semantic graph comprises nodes representing concepts and edges representing relationships between concepts of connected nodes and wherein each edge is weighted with a semantic similarity value, wherein determining the probability that the candidate user is interested in the item of content comprises: responsive to determining the plurality of user-stated concepts of interest and the plurality of concept tags do not intersect, determining a path from a given user-stated concept of interest and a given concept tag in the weighted semantic graph; and determining a weight of the path from the given user-stated concept of interest and the given concept tag; and responsive to the probability exceeding a probability threshold, delivering the item of content to a client data processing system of the candidate user.