The internet copies everything, so how does one make money selling free copies? Kevin Kelly has a great article on this topic. His simple answer is:

When copies are super abundant, they become worthless.
When copies are super abundant, stuff which can't be copied becomes scarce and valuable.

And he discusses eight things that can't be copied:

1. Immediacy,
2. Personalisation,
3. Interpretation,
4. Authenticity,
5. Accessibilty,
6. Embodiment,
7. Patronage, and
8. Findability.

Thanks to uberblogger Seth Godin for finding the article for us.