A commentary about duplicate publications, entitled: A tale of two citations, was published by Mounir Errami & Harold Garner in Nature 2008(24 Jan); 451(7177): 397-399, doi:10.1038/451397a. The summary:
Are scientists publishing more duplicate papers? An automated search of seven million biomedical abstracts suggests that they are, report Mounir Errami and Harold Garner.
A copy of the commentary, with appropriate attribution, has recently appeared via a blog post, Research Plagiarism, News Bioteknologi, June 1, 2008.
For a news item about the commentary, see: Discovering and deterring duplicate publications, Peter Suber, Open Access News, January 25, 2008.
A related topic is plagiarism, where a duplicate version is improperly attributed to the plagiarist. The easiest kind of plagiarism to detect is plagiarism from OA sources. And, for this reason, plagiarists might choose to aim for obscurity, in order to minimize the odds of being caught. This has been pointed out, for example, by Heather Morrison, in The Plagiarist, and Aiming for Obscurity, The Imaginary Journal of Poetic Economics, February 23, 2008, and by Peter Suber, in Aiming for obscurity, Open Access News, February 24, 2008.
The source of the phrase “aiming for obscurity” is another blog post by Heather Morrison, in The Imaginary Journal of Poetic Economics, February 23, 2008. The phrase “aiming for obscurity” was, in turn, inspired by this blog, Be Openly Accessible or Be Obscure.