The FDA’s letter to 23andMe calls “particularly concerning” the information the tests would provide about the gene linked to breast cancer (BRCA) “because of the potential health consequences that could result from false positive or false negative assessments.”
According to 23andMe's site:
"You should not change your health behaviors solely on the basis of information from 23andMe. Make sure to discuss your Genetic Information with a physician or other health care provider before you act upon the Genetic Information resulting from 23andMe Services. For most common diseases, the genes we know about are only responsible for a small fraction of the risk. There may be unknown genes, environmental factors, or lifestyle choices that are far more important predictors. If your data indicate that you are not at elevated genetic risk for a particular disease or condition, you should not feel that you are protected. The opposite is also true; if your data indicate you are at an elevated genetic risk for a particular disease or condition, it does not mean you will definitively develop the disease or condition. In either case, if you have concerns or questions about what you learn through 23andMe, you should contact your physician or other health care provider."
(Paraphrased from Harry Binswanger's article: http://onforb.es/1iQEN4U)