Vast Study Casts Doubts on Value of Mammograms

This is an article about a research study into the value of mammograms over breast exams by a trained medical professional.  This article was published in the New York Times on February 11th.  A link to the study itself can be found within the text of the article.

1) What is the value in a study of the size and magnitude such as this?  Does the size of this study give it more weight within the medical community?  What is the value of this study being longitudinal in nature instead of retrospective or cross-sectional (existing statistics based)?  How might this change its perceived value to the medical community?

2) The results of this research seem to go against mainstream recommendations.  Were there any factors that might have led to the researchers having a bias against mainstream medical recommendations?

3) What was the researcher’s purpose in conducting this study?  Were they trying to evaluate the efficacy of mammograms or promote a change in the medical system?  How might the purpose of the study changed the procedural aspects of the study?