The code to update the current "Now Playing" playlists is generating INSERTS into mysql, not UPDATE, which will add an item to the tracks table every time a song is played.

                     73 Query       INSERT INTO tracks (content_type, remote, tag, title, titlesearch, titlesort, url) VALUES ('cpl', '0', '1', 'Now Playing - Livingroom', 'NOW PLAYING LIVINGROOM', 'NOW PLAYING LIVINGROOM', 'clientplaylist://00:04:20:05:ce:48')


mysql> select count(*) from tracks where content_type =  'cpl';
+----------+
| count(*) |
+----------+
|      316 |
+----------+
1 row in set (0.01 sec)


This should probably be an update.  (Hrrm.. not sure why it isn't  ... I thought the url field was Unique...)