A friend of mine purchased a track and I copied it to my machine over the network. Then I disconnected my Mac from the internet by pulling the ethernet plug and tried to play the track.

It said I was not authorized to play it, and would I like to authorize it. My friend entered his account name & password to authorize, after which we got a dialog that the Music Store could not be contacted.

SO... if you have an unauthorized AAC, you must have a network connection to authorize. This is how they track the three machines.

I believe once the track has been authorized, you no longer have to be connected to the net to play it. We didn't actually test this, now that I think about it, but I highly doubt it goes out on the net every time you play one of the purchased files.

My biggest concern is can I "bulk authorize" tracks if I, say, buy a new Mac and need to transfer a few hundred tracks to it?