From http://bugs.debian.org/513291

 "In mpd.conf, the "admin" permission covers updating the db and
 killing mpd.

 "Since there are quite some usecases in which the user can upload
 music to the mpd's directory by means of anonymous FTP or so, it is
 desirable that any user may issue a db update, while killing the mpd
 should not be possible.

 "I'd suggest to remove the db update from the admin group and either
 add it to "control" or an own group."