An interesting article on plagiarism from Ars Technica, Plagiarism and falsified data slip into the scientific literature: a report, by John Timmer (August 07, 2007):
Scientific progress is conveyed primarily through peer-reviewed publications. These publications are the primary source of information for everyone involved in scientific research, allowing them to understand the current scientific models and consensus and making them aware of new ideas and new techniques that may influence the work they do. Because of this essential role, the integrity of the peer review process is essential. When misinformation makes its way into the literature, it may not only influence career advancement and funding decisions; it can actually influence which experiments get done and how they are interpreted. Bad information can also cause researchers to waste time in fruitless attempts to replicate results that never actually existed.