23. A system comprising: one or more computers, the one or more computers implementing: a dataset tool to identify a comparison vector x, and a set of candidate vectors corresponding to the vector x; a similarity tool to determine a similarity estimate between the comparison vector x and each candidate vector y in the set of candidate vectors corresponding to x, where the similarity estimate is based on: a sum of a similarity between a set of processed features of the comparison vector x and a set of processed features of the candidate vector y, and a product of a minimum size of at least one of the candidate vector x or a set of non-processed features of the candidate vector y, and a similarity score between a maximum weight of the comparison vector x and a maximum weight of the candidate vector y; and determine a similarity score between the comparison vector x and each candidate vector y for which the similarity estimate meets a similarity threshold; and a results tool to include a new pair of vectors comprising the comparison vector x and the candidate vector y for each candidate vector y in a list of similar pairs of vectors if the similarity score meets the similarity threshold.
23. A system comprising: one or more computers, the one or more computers implementing: a dataset tool to identify a comparison vector x, and a set of candidate vectors corresponding to the vector x; a similarity tool to determine a similarity estimate between the comparison vector x and each candidate vector y in the set of candidate vectors corresponding to x, where the similarity estimate is based on: a sum of a similarity between a set of processed features of the comparison vector x and a set of processed features of the candidate vector y, and a product of a minimum size of at least one of the candidate vector x or a set of non-processed features of the candidate vector y, and a similarity score between a maximum weight of the comparison vector x and a maximum weight of the candidate vector y; and determine a similarity score between the comparison vector x and each candidate vector y for which the similarity estimate meets a similarity threshold; and a results tool to include a new pair of vectors comprising the comparison vector x and the candidate vector y for each candidate vector y in a list of similar pairs of vectors if the similarity score meets the similarity threshold. 53. The system of claim 23 in which each vector represents a corresponding user in a community, and each feature of each vector represents a preference of the corresponding user towards an object in a set of objects.