1. A method for recommending media on a social-software website, comprising the operations of: creating a neighborhood using a map-reduce architecture by pair-wise application of a similarity measure to a sparse matrix of users and items of media designated by the users, wherein the sparse matrix is derived from a log; identifying an item of media that has been designated by a first user in the neighborhood but not a second user in the neighborhood; rating the item of media, using a weighted vote of the users in the neighborhood, wherein the weighted vote depends at least in part on the mean similarity of the users in the neighborhood who have designated the item of media; and recording the item of media as a recommendation for subsequent presentation to the second user in a view in a graphical user interface displayed by a browser, if the rating of the item of media is among the highest in comparison to the ratings of other items of media designated by users in the neighborhood, wherein each operation of the method is executed by one or more processors.