1. A method for providing targeted content to users based upon tagged search results, comprising: maintaining a set of personal tag collections for a first user, the set of personal tag collections comprising a first personal tag collection comprising one or more tagged search results tagged by the first user with a first tag; identifying a first topic of interest for the first user based upon the first tag; providing first targeted content to the first user based upon the first topic of interest; generating a second personal tag collection comprising one or more tagged search results tagged by the first user with a second tag; representing the set of personal tag collections as one or more bi-partite graphs; and traversing the one or more bi-partite graphs to determine that the first personal tag collection corresponds to a category and that the second personal tag collection corresponds to the same category.