Ok I am working on a social network for artists, writers, musicians etc...I have been sitting here thinking about copyright issues. While majority of the people who will sign up to the site will be genuine artists/writers, sadly there will be some people there who will put up other people's work and pass this off as their own. Their will be a shop element to it where artists/writers/musicians can sell their work on the site and I make a nominal fee. I am looking for advice because I am not too sure how to prevent infringement of copyright. Any ideas?