6. A system for categorizing items, the system comprising: a data store that stores a plurality of hierarchically organized categories for items, each of the hierarchically organized categories represented by at least one category attribute and corresponding category attribute value; and an item categorization service in communication with the data store, the item categorization service configured to: receive item information for an item of interest, the item information comprising at least one item attribute and a corresponding item attribute value for the item of interest; assign a first category for the item of interest from first categories of the hierarchically organized categories stored by the data store; identify a category attribute of the assigned first category; obtain at least one second category that comprises the identified category attribute and corresponding category attribute value; determine one or more second category candidates based at least in part upon an assessment of the relevance of the item information with the at least one second category; and assign one of the second category candidates as a second category for the item of interest based at least in part upon the hierarchical positions of the one or more second category candidates with respect to one another such that at least one of the remaining second category candidates is a sub-category of the second category.
10. The system of claim 6 , wherein at least one of the first categories does not comprise the identified category attribute of the assigned first category.