"Experts Predict No Better Than Non-experts".
Here are the links to my series of posts on Turnitin, plus a list of plagiarism resources and two others related to reasoning: The chart provides information ranging from price to support to much more, including the issue of intellectual property. On a side note, at the Educause 2007 Southeast Regional Conference in Atlanta, Liz Johnson, Project Manager, Advanced Learning Technologies (Board of Regents of the University System of Georgia), had a poster session with a chart (pdf) that compared seven software detection programs:Turnitin, MyDropBox, PAIRwise, EVE2, WCopyfind, Copåatch, and Glatt.
At least this approach, unlike quite a bit of the ideological controversy surrounding these tools, is one that is simply being practical. Not knowing German, I can't read the report to see what percentages of "finding" were found, and it seems odd to me to expect that any software would discover "all plagiarisms." Of course, users should consider whether the software is worth the money, depending, I imagine, upon some expected percentage of successful discovery-especially if you want to use it as a learning tool in the classroom. But our summary for 2007 is the same as for 2004: It is better to use a search machine yourself, the software just costs money and is not necessarily very good at finding all plagiarisms. We hope that our work can help these companies to produce better results. She and her colleagues released a report (in German) on the testing of these services. It's maintained by Debora Weber-Wulff, professor for Media and Computing at FHTW Berlin, who has been conducting research on plagiarism detection services. This blog on plagiarism, Copy, Shake, Paste may be of interest.