It looks like the New England Journal of Medicine published a lung cancer screening study in which the authors failed to disclose that they were funded by GE, the makers of the CT scanners that the study reported to be useful in detecting early lung cancer in smokers.
This sort of practice is highly unethical, even when the outcome is supposedly "good" (screening for cancer).
Here is a link to a blog about the topic in the Boston Globe:
http://www.boston.com/news/science/articles/2009/01/12/new_england_journal_changes_policies/Omai