When downloading or extracting large files, tracker will add multiple copies to the database.

$ ls -l /home/iain/Music/Nuclear\ Heart/Transmission\ Towers\ Collapsed\,\ Communication\ Down/
total 180848
-rw-r--r-- 1 iain iain 110153883 2010-02-18 13:22 01 Transmission Towers Collapsed.mp3
-rw-r--r-- 1 iain iain  74948136 2010-02-18 13:22 02 Communication Down.mp3
-rw-r--r-- 1 iain iain     71630 2010-02-18 13:22 cover.jpg

with this query:
SELECT ?uri nie:url(?uri)
WHERE
{ ?uri a nmm:MusicPiece }

tracker-sparql -f /tmp/tracker-test | grep Nuclear
  urn:uuid:597f5d15-738b-81c3-13ed-e55375110ee9, file:///home/iain/Music/Nuclear%20Heart/Transmission%20Towers%20Collapsed,%20Communication%20Down/01%20Transmission%20Towers%20Collapsed.mp3
  urn:uuid:a28b9114-1b19-9908-b36c-c86ffbe92e88, file:///home/iain/Music/Nuclear%20Heart/Transmission%20Towers%20Collapsed,%20Communication%20Down/02%20Communication%20Down.mp3
  urn:uuid:02efb4ad-8b72-4945-d2ef-673be1ea41da, file:///home/iain/Music/Nuclear%20Heart/Transmission%20Towers%20Collapsed,%20Communication%20Down/01%20Transmission%20Towers%20Collapsed.mp3
  urn:uuid:6703e884-cd95-6b44-e194-23a5041e4571, file:///home/iain/Music/Nuclear%20Heart/Transmission%20Towers%20Collapsed,%20Communication%20Down/02%20Communication%20Down.mp3

Gives two entries for each track, each with a different uid. The tracks were extracted from a zipfile and are quite large, but I've seen it happen for large downloaded files as well.