By now it is obvious that iTunes 4 is a smash hit with the peeps, but a new problem is forming. The new software allows users to share their library with others by streaming the songs. This means that you can't copy the tracks, just listen to them. Obviously this was meant to keep people from illegally file-swapping. That has all changed.
Enter in iLeech and iTunesDL (download here). The first is a sourceforge project and the second has yet to be claimed by anyone, as far as I can tell (the link is to one of the early links). These two programs allow you to enter in the location of a stream and download tracks from others' iTunes library. Bring together iTunes, either of these programs and Spymac Music/Share iTunes and you have access to millions of MP3s.
The new question, is what will happen next? The RIAA cannot be happy and Apple now has to make a big decision. Kottke believes that Apple must have know what was going to happen in advance but I don't know if I agree. Then again, this happened so quickly it must have been relatively easy to figure out.
It seems the best option will be to remove the option of broadcasting your iTunes library over the internet and only allow it via Rendezvous. You could still download files from those on your network but you wouldn't be able to browse thousands of libraries. I'm quite excited to find out what happens next.