I.P. – There is little to no need for the honor system when transferring AAC files. AAC files can only be played on computers that are authorized by the account that purchased them. I needed to sell my account to the buyer in order for him to play it on his computer.
While I could have left my computer authorized to play the song, their support document claims that users can have Apple manually deauthorize computers that they don’t have access to.
As for the iPod, an iPod is linked to a specific installation of iTunes. If I load up my iPod at home it will have all the songs on my home computer. If I then bring it to work and plug it into my computer there it will ask if I want to associate the iPod with my work computer, which would delete all the songs currently on the iPod.
So I suppose you could buy an iPod just to listen to the songs that I purchased (and that seems completely within their DRM’s rules) but that scores even higher on the impracticality scale than what I did.