Even if there were no illegal ...

Even if there were no illegal copying, the advent of digital distribution will put a lot of stress on the movie and music industry. When the distribution costs comes down, that puts more price pressure on the rest of the cost.
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 Edward Felten

Quotes from the same author

Given that you'll never be able to prevent copying, the question is, what can you do to minimize it? What can you do to make consumers happy enough with legitimate use of the system that they'll be willing to pay for it?
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 Edward Felten
Vigorous enforcement of copyrights themselves is an important part of the picture. But I don't think that expanding the legal definition of copyright outside of actual copyright infringement is the right move.
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 Edward Felten