1. A computer-implemented method comprising: calculating a probability distribution of a set of items with respect to latent variables including determining counter values incremented in response to user selections of items in the set of items and according to user membership in categories represented by the latent variables, where each counter value corresponds to a category of which the user is a member, and where each counter value is fractionally incremented relative to other categories of which the user is a member; clustering a plurality of users with respect to the one or more latent variables in a probability distribution model of a relationship between a set of users and a set of items, the probability distribution model comprising the calculated probability distribution of the set of items with respect to the latent variables; and generating a relationship score for one or more items in the set of items, each relationship score relating the item to a particular user in the set of users based on the particular user's category memberships and the calculated probability distribution of the set of items with respect to the latent variables.