11. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: identifying websites with which users of a social networking service have established an affiliation; filtering the identified websites by removing websites in which a count of users who have established an affiliation with the website exceeds a threshold, the filtering producing a plurality of filtered websites; producing a list of valid affiliations for each filtered website, comprising: generating a validity score for each of the established affiliations with the respective filtered website, determining whether each of the established affiliations with the respective filtered website is valid based on the corresponding validity score, and ranking the users who established valid affiliations with the respective filtered website based on the corresponding validity scores; and providing the list of the valid affiliations ordered by the ranking.
11. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: identifying websites with which users of a social networking service have established an affiliation; filtering the identified websites by removing websites in which a count of users who have established an affiliation with the website exceeds a threshold, the filtering producing a plurality of filtered websites; producing a list of valid affiliations for each filtered website, comprising: generating a validity score for each of the established affiliations with the respective filtered website, determining whether each of the established affiliations with the respective filtered website is valid based on the corresponding validity score, and ranking the users who established valid affiliations with the respective filtered website based on the corresponding validity scores; and providing the list of the valid affiliations ordered by the ranking. 18. The system of claim 11 , wherein generating the validity score comprises determining a user quality score, the user quality score based on a popularity of a corresponding user.