2. The system of claim 1 , wherein the item relationship data comprises item-to-item similarity mappings.
2. The system of claim 1 , wherein the item relationship data comprises item-to-item similarity mappings. 3. The system of claim 2 , wherein the item-to-item similarity mappings are based, at least in part, on tag-based item similarities detected by analyzing aggregated tag data of a population of users.