The application fetches the "recent tracks" journal from a Last.fm user.  The journal must be made public by the user.  Each journal entry is kept in a local database (in ~/).  The application then sifts through the journal entries and updates the a table of "unique tracks" in the local database.  Lastly, the application fetches the MBID (musicbrainz identifier) associated with each "unique track" thereby facilitating the correlation between a local music file and remotely scrobbled ones (e.g. from an iPod).

The application shows a "Tracks to update" indicator:  the number of tracks left to process before entering a "dormant state".  The indicator "Last.fm Recent Tracks" is just an approximation.

Finally, the application fetches the complete journal information at regular intervals: this behavior is necessary as I found that Last.fm sometimes hick-ups... 

This application works best in conjunction with musicbrainz-proxy-dbus.

This application requires that Rhythmbox's Last.fm be configured with the user's Last.fm account information.

If the a "403 forbidden message" appears in the user message box, it is probably due to the privacy settings associated with the Last.fm user account.