This is my response to this Ars Technica article.
If you look at all of the foundational arguments for copyright, they are about a benefit to society, while only secondarily being about the authors or creators. Since the beginning, copyright, or a monopoly on ideas, has been regarded as an acceptable evil in the pursuit of the creation of new works. Copyright, like any enforcement strategy in a social-contract-based form of government, is a deal between the governors and the people which is only acceptable if the restrictions on personal autonomy are outweighed by the benefits that the restrictions bring.
Currently, there is little thought given to whether a copyright term that extends 70 years after the author's death actually makes the author more likely to produce a new book. Whether or not "Steamboat Willy" is still restricted by copyright has little bearing on whether Walt Disney produces more cartoons, because he is dead. According to the constitution and every western (possibly others as well) system of copyright ever, the term of a copyright must not be one second longer than is required to induce a creator to produce new works. The author's "property right" has never been a basis of copyright law and was even explicitly rejected by the Supreme Court of the US in 1985.
The problem nowadays is that wealthy corporate interests (not to beat the "rah, corporations r teh evil!!!11" drum too much) have a large vested interest in extending the copyright term as long as possible. Since their primary motive is profit, they don't care whether the money they make is on new creations or the back catalogue; they are perfectly content to resell "Snow White" over and over indefinitely, regardless of whether doing so encourages the production of new works. Indeed, a compelling argument could be made that continuing to sell 50+ year-old works actually decreases the incentive to produce new works, as it crowds out any new content and reduces the money available to finance new creations.