1. A non-transitory computer-readable medium embodying a program executable in a computing device, the program, when executed by the computing device, directing the computing device to at least: receive a request for a product search corresponding to a search query; perform the product search in accordance with the search query to produce a plurality of initial product search results; identify a most relevant product search result of the plurality of initial product search results; include in a plurality of filtered product search results the most relevant product search result; identify other product search results in the plurality of initial product search results that are similar to the most relevant product search result based at least in part on item similarity data derived from behavior-based search data; discount a relevance score of the other product search results; repeatedly discount the relevance score until a search diversity score associated with the product search is improved by a predefined threshold; and provide the plurality of filtered product search results in response to the request.