I'm building a website for a comedian who, amongst other things, wants to sell his material online. Rather than selling a CD and having the hassle of posting it out, I want to persuade him that he should sell it in digital format online. The problem is that he's worried about people emailing friends their favourite tracks. The other problem is that, apart from being a consumer myself, I don't know much about how copy protection works! I presume that there's no easy way of just creating copy protected files for people to download from the website, as they'd need to have people's ID embedded in them somehow, rather like songs from the iTunes store require your Apple / AOL ID to unlock them? Are there any services that people know of / have used to distribute copy-protected audio? Or am I wrong in assuming that you can't just make copy-protected audio files for download from a website?