Ghostwriting is a pretty hot topic in the scientific community at the moment. A study has just been released by The Journal of the American Medical Association detailing how widespread ghostwriting is in the medical community. This follows the revelation in the New York Times in August that a major pharmaceutical company in the US had used ghostwriters to write review papers highlighting the benefits of hormone replacement therapy in women and downplaying the risks. This was done between 1998 and 2005, although the court records have only just been released. Since then the guidelines have been updated, as you can see in this article written back in 2006 by the BMJ.
The danger of using ghostwriters in this way is that general practitioners and others reading these reviews for peer guidance may not be aware that a drugs company has been involved in their production, in some cases paying for the medical ghostwriter's services.
You can read the New York Times article here.