This is a simple one, iTunes purchased music should be able to be transferred from an iPod. If I accidentally delete a song file, or my hard drive crashes I should be able to restore any iTunes purchased music back to my computer from my iPod, that just seems fair.
This is one of a handful of issue that has really kept me on the sidelines of purchasing digital music. I work in IT and I see hard drives fail all the time. So purchasing music that would be totally lost if my hard drive failed seems like a really bad idea. Sure I can make a backup, but what a hassle, especially when the iPod could serve as a backup device. Obviously this still wouldn't be perfect, but it's a pretty good start especially given people don't make regular back-ups of anything. If Apple and the music industry want people to invest in legal music downloads they need to enable a music collection last a lifetime.
But to me the real issue is that I can't think of a good reason to not allow customers to do this. If FairPlay determines who is authorized to play the file, it should be able to allow transfers from an iPod if the computer is authorized. If anyone can come up with a reason that something like this would compromise Apple's FairPlay please add a comment.
More about FairPlay from Wikipedia.