You pay for your music. You don't make copies of it for other people. If you want to sell music that you own, you don't keep a copy for yourself. If two, or more, people are listening to your music at the same time, you've stolen the extra copy.
i'm about to start buying mp3s legally i was wondering, how does it work if you were going to lend an mp3 CD to a friend. i mean, you'd basically MAKE them the CD, and then by faith everyone assumes they won't copy it, and that they'll eventually throw away or give back the CD. ALSO, you'd still have the mp3s on file and be able to listen to them youself and burn them for yourself, so, it's just kinda weird. i have a friend who probably wouldn't accept any CD-R with music on it unless she knew it was completely legit. i like the way she thinks and it's making me realize i need to legitamize my mp3 collection.