1. A method for facilitating media playlist generation for a program participant using similarity ratings that indicate similarity between pairs of media items based at least in part on how often the pairs co-occur in media libraries of other program participants, the method comprising: transmitting, from a program participant's client device, data representative of a media inventory in a media library of the program participant, wherein the data includes first-identification data of a plurality of individual media items presently contained in the media library of the program participant; and receiving, by the program participant's client device, similarity ratings for the plurality of individual media items, the similarity ratings compiled based on cumulative data collected from a plurality of other program participants, wherein the cumulative data includes second identification data of the plurality of individual media items also contained in media libraries of the plurality of other program participants, wherein the first and second identification data are different, and wherein the compilation of the similarity ratings further includes processing the cumulative data to: associate respective individual media items of the plurality of individual media items presently contained in the media library of the program participant and also contained in the media libraries of the plurality of other program participants with a unique identifier based on the first and second identification data; determine a frequency that pairs of the plurality of individual media items co-occur in the media libraries of the plurality of other program participants, determine an overall occurrence of each of the plurality of individual media items in the media libraries of the plurality of other program participants, and assign the similarity ratings between the pairs of the plurality of individual media items based on the determined frequency of co-occurrence and the determined overall occurrences.