There seems to be 2 distinct trains of thought about sharing these tracks.
Those who bought the iPod and have paid a considerable amount of money for these tracks don't really see it as fair of ethical to share these tracks as they paid and others did not. While it is being done through Apple, it is still now RELEASED material and is available for purchase to the general public. In not buying this from Apple/U2 it is now illegal to share and in breach of copyright rules.
The other train of thought is that this is U2 music and ALL U2 fans should have fair access to these tracks. In putting a substantial price tag on the vehicle used to download the music....and a substantial price tage on the music itself, those fans without the financial means to purchase this "exclusive" music are left without.
This is creating a division amoungst U2 fans with and without the financial means. It is also creating an ethical dilema for those who don't want to impact the band through copyright violation but have no other choice in order to hear these unreleased songs.
The last time I checked, this was a community of fans dedicated to the perpetuation of the greatest band alive.
Once you have decided which side you are approaching this issue from, you need to remember we all share a common bond in our love of U2. Share freely, turn your back and ignore, point fingers, or report people. Do what you feel you have to do.
Before you do anything....remember why you joined in the first place.