Yesterday, I had a message for Jack Shafer. Here's a little more info (that, obviously, confirms my point) on the same subject.
It comes from a study (800K PDF, in French) from the Chaire en relations publiques de l'Université du Québec à Montréal.
When asked to characterize the work of PR officers, 50% (42.86+7.14%) of the journalists interviewed said that PR flacks helped get them access to information while only 29.59% (17,35%+12.24%) said that they hindered access to information. Other answers (including has no impactInfopresse wrote an article on the subject and Nadia Seraiocco added her comments (both in French).