The Summer 2010 online issue of "Issues in Science and Technology Librarianship" includes a nice viewpoint by Edward J. Eckel entitled "A Reflection on Plagiarism, Patchwriting, and the Engineering Master's Thesis":
"How many times has a graduate student asked you questions such as the
following: "How many words do I need to change so I'm not plagiarizing?"
or "If my professor gives me his article or patent and tells me to go
ahead and 'use it', do I need to cite it?" Such questions indicate a
profound need for clarification of issues like plagiarism and
attributing sources. This need is a result of a disconnect between
expectations for graduate students in the sciences and technology, and
how they are being educated to meet those expectations. [...]
Rather than focusing on punishment or ethics, we librarians and faculty
members need to teach these students a more realistic view of the
writing process, one that allows and encourages the reuse of generic
strings of text and yet scrupulously attributes the ideas and
distinctive written expressions of other authors."