For anyone who is even remotely interested in the movement to prevent overdiagnosis, I suggest you check out this article, How to Prevent Overdiagnosis, in its entirety.
Dr Arnaud Chiolero et al. have provided a thorough overview of the causes of overdiagnosis, methods to estimate the frequency of overdiagnosis, and interventions to prevent overdiagnosis.
As a teaser, I present to you the summary tables from the article:
We all might argue about the exact contributors to overdiagnosis, but this list (based on a review of the literature) is pretty thorough. Fortunately there is hope to combat the problem, and some specific examples are given: