@Glyn Moody Thanks for citing my article at QuestionCopyright.org.
@Eo Nomine Thanks for your thoughtful comments.
1) You've clearly never heard of moral rights / droit moral, which is prevelant n civilian jurisdictions (and several commonwealth jurisdictions like Canada) and protects THIS VERY THING (primilarily right of attribution & right of integrity). Abolishing copyright eliminates these rights for academics in countries that have them.
I think most people who advocate reforming or abolishing copyright would like to keep the right of attribution and right of integraity in place. For example, Depoorter Ben, Holland Adam, and Somerstein Elizabeth, “Copyright Abolition and Attribution”, Review of Law & Economics 5, no. 3 (December 31, 2009), http://www.bepress.com/rle/vol5/iss3/art5.
2) If copyright serves no useful purpose for academics, there is absolutely nothing stopping any academic or institution from releasing all of their research papers under an open access license or even dedicating it to the public domain. Suggesting that the whole system must be abolished to cater to a small, specialized segment that doesn't require it's protections when that same segment can opt out of the system voluntarily is non-sensical... It's like suggesting we abolish car insurance because people who don't drive don't need it, even when they're not required to get it (and suggests that this is more about the author and QuestionCopyright's anti-copyright agenda than about helping academics).
Most scholars are not familiar with the copyright debate. Their primary concern is to get their works published and when the publishers ask them to sign whatever copyright agreement before they can publish their works, they usually do so without giving much thought to it. Recently, efforts are made to encourage scholars to add additional clause to the copyright agreement so they can legally share their own works with the general public. (e.g. SPARC Author Addendum) Nevertheless, authors may get apprehensive about this sort of legal details.
On the other hand, we do see quite a few academic authors who post their papers on their own websites and these papers are indexed by Google Scholar, which links the papers to such PDF files provided by the authors. In this way, the public may access the papers free of charge. Technically, the authors are breaking their copyright agreement with the publishers by doing this under the current copyright system.
Of course, academic paper is only a small segment of the copyrightable subject matter. Yet, we can only deal with one thing at a time. Software developers have long been battling to free their works from copyright restriction. And others have contributed user generated contents to sites like Wikipedia under Creative Commons. Even the newspaper and magazine articles have become freely available online competiting for the attention of readers. So the trend is pretty clear: with the digital technologies, more literate works have become freely accessible. With a great amount of public attention diverted to the FREE stuff online, academic papers may become increasingly obscure and the academic community more and more marginalized as a result of copyright restriction.
3) "More readers able to access more works would mean a greater likelihood that unacknowledged copying between them would be noticed and exposed." Really? Do we know that more people read access open access materials than traditionally published materials accessible via proprietary databases? Do we know if they detect plagiarism more often? This is a pretty bald assertion to make without any actual facts to back it up. Again, it's nonsensical to call for all of copyright to be abolished merely because there is a "likelihood" that more plagiarism might possibly be detected theoretically (funny that copyright opponents constantly complain that copyright policy is not sufficiently evidence based but seem to have no problem making their own assertions based on suppositions without any actual facts to back them up).
I am not aware of any empirical studies that may prove or disprove the claim that removing copyright restriction will reduce plagiarism. But consider the machanism of Turnitin, the largest software system for plagiarism detection. Basically, Turnitin takes the papers under review and checks them against a database of published papers the authors may copy from using natural language processing. The trouble with Turnitin is that, to avoid criticisms about copyright infringement, they keep the users in dark with regard to what database they use. An alternative to Turnitin would be to build an open-source plagiarism checking system that is free for all teachers and students. And to do that, we need open access to all academic papers in machine-readable forms.
So the case for plagiarism reduction is not about how many human readers will detect the cases of plagiarism but whether or not we can build a software sytem to do it. We have all the technologies available but copyright is the main obstacle.