Many people are taking fish oil for it's touted benefits of reducing inflammation, supporting cardiovascular health and supporting mental health.  Unfortunately, more and more studies are questioning the benefits of fish oil, and even worse is that recent studies are reflecting significant risks of taking fish oil.  One such study is suggesting increased risk of prostate cancer (aggressive prostate cancer at that), and this study confirms two earlier studies.  You can read about that study here:

http://health.usnews.com/health-news/news/articles/2013/07/10/too-much-fish-oil-might-boost-prostate-cancer-risk-study-says

Another article critical of fish oil written by Dr. Ray Peat can be found here:

http://raypeat.com/articles/articles/fishoil.shtml