Yes, YASN (Yet Another Social Network). Have you noticed that Add as a friend is the most common link in websites created these days?
Anyway, this time we have SongBuddy. Social software + online music: an explosive pair!
SongBuddy is a new way to find music that’s already available on the Internet. By finding songs on bands’ and labels’ sites and sharing the address of those songs with your friends, you can explore music you’ll love that you wouldn’t hear anywhere else. So sign up, make some friends and list some music. You won’t even need to install any software, SongBuddy works with your current media player.
Here my profile.
SongBuddy also produces a FOAF file representing your friends and uses the MusicBrainz RDF namespace.
The term of service is also very good!
Unless otherwise specified, all content on this site is copyright SongBuddy LLC. You may use the data on this site under the Attribution-NonCommercial-ShareAlike 1.0 Creative Commons license.

Another similar site worth mentioning is Webjay by Lucas Gonze but I haven’t had time to try it yet.

This post also appears on the open channel playlistlogging