CNET: Using a visible menu item is hacking
It doesn't take much of a "Hacker" to find the "Connect to Shared Music..." command near the top of the Advanced menu in iTunes. Finding out what the URL format was and what the port used is also wasn't much of a hack.
And you still can't copy music, only listen... unless of course, you plug a cable from your line out jack to your line in jack and re-record the sound, but that's a PITA and doesn't include the music's metadata and requires a lot of work to cut properly.
CNET said, "Apple itself did not release documentation on the over-the-Net sharing features and does not officially support the efforts."
If Apple didn't want this to be used over the internet, why did they put a Connect to Shared Music menu command in the iTunes menu bar? The only way to use that is to enter a daap URL, and if you know how to form a daap URL, it's hardly a stretch to try an IP address that isn't on the local subnet. If they didn't want iTunes to be shared outside of the subnet, they wouldn't have put this command in, they would have only exposed it via Rendezvous.
Oh, and as usual, Bill has great coverage of this too. :-)