26. A system comprising: one or more computers, the one or more computers implementing: a dataset tool to identify a comparison vector x having processed features and non-processed features, a first set of vectors, each vector in the first set of vectors having processed features and non-processed features corresponding to the processed features and non-processed features of the comparison vector x, and a candidate vector y from the first set of vectors; and a similarity tool to determine a similarity threshold, and a maximum similarity between the non-processed features of x and the non-processed features of y; wherein the dataset tool removes the vector y from the first set of vectors if the maximum similarity does not meet the similarity threshold.
26. A system comprising: one or more computers, the one or more computers implementing: a dataset tool to identify a comparison vector x having processed features and non-processed features, a first set of vectors, each vector in the first set of vectors having processed features and non-processed features corresponding to the processed features and non-processed features of the comparison vector x, and a candidate vector y from the first set of vectors; and a similarity tool to determine a similarity threshold, and a maximum similarity between the non-processed features of x and the non-processed features of y; wherein the dataset tool removes the vector y from the first set of vectors if the maximum similarity does not meet the similarity threshold. 35. The system of claim 26 in which each vector in the set of vectors represents a corresponding user in a community, and each feature of each vector represents the corresponding user's click-behavior with regard to a content item.