I am a programmer and an active DJ myself and as such a type of person I do a lot of music organizations into different playlists. For example, each month on Soundcloud I keep one playlist of "Mixes to listen" (usually private) and one playlist of "Favorite mixes for month X". I've been doing this for a few years already. You can find these at https://soundcloud.com/ulterior

I can see how this kind of a service can be useful, especially in recommendations, if you are able to answer what music did the digger like from his diggs. Because, as we musicheads well know, not everything we dug out is gold.