Digital goods libraries are compared via their datasets, which include organizational data and history data. Potential comparison results include a shared multiple natural languages presence, shared genre frequency change, shared artist frequency change, shared digital good frequency change, shared outlier presence, shared similar songs presence, and/or shared recommendable goods presence. Proper subsets of datasets may be specified by playlist, genre, artist, category, date, play frequency, and/or play count, and then compared. Comparison results may be visualized, such as playlist content over time, play frequency over time, and/or play count over time. Some results include printed or spoken text such as an artist name, actor name, author name, genre name, and/or review content. Control over disclosure of library owner identity is provided. In some cases a dataset is compared with multiple datasets in a group, e.g., to help assess compatibility between a prospective member and current members of the group.