This is a classic reference that reminds us that even with all the objective methods developed for systematic overviews, there is still a core of choices that are largely subjective.
Susan Mayor. Row over breast cancer screening shows that scientists bring some subjectivity into their work. BMJ. 2001;323(7319):956. DOI: 10.1136/bmj.323.7319.956. PMCID: 1121506
You can find an earlier version of this page on my blog.