Lala.com and complex logic

I like listening to music while I work, and I like having all of my music at my fingertips. It used to be that I had to literally have a full copy of all my music on my work computer, until I found this cool service called Lala. It's a music service where I can have an application scan my home collection, and then play any song I own in my web browser, instantly making my entire collection available from anywhere.

Check it out: lala.com

I've been curious as to how exactly it handles the matching of the song I own to the song they have in their database. It appears that some songs just match, and others don't match, and they then upload the file into my account, so it's still available to me. Most curious is when it matches 5 songs from an album that has 10 songs. I would think it would match all of them, but maybe they only have the most popular five songs from that album in their database.

Anyways, I had scanned my library a while ago, and listening to different albums for the last few weeks, with no complaints what-so-ever. Today I started listening to Green Day's American Idiot. I was suprised to find that while the first two songs were the album versions, the third song, Holiday, was actually a live version from another album. I guess the matching logic still needs a little refining.