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 user-stated concept of interest; determining a probability that the candidate user is interested in an item of content based on a semantic similarity of the user-stated concept of interest and a concept tag 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; and responsive to the probability exceeding a probability threshold, delivering the item of content to a client data processing system of the candidate user.