John Lauerman reports in BusinessWeek on his experience participating in the Personal Genome Project:
“This is probably the most serious variant that we’ve actually seen to date in the study,” Thakuria said. About two out of 1,000 people have the JAK2 variant, which encourages blood cells to grow and divide. The variant is used to diagnose three rare blood disorders, including primary myelofibrosis, which is potentially lethal. “I don’t want you to fret about this,” Thakuria said, before giving me fresh cause for worry: a study, published in 2010, in which 10,507 people in Copenhagen gave blood samples and were followed for as long as 18 years. The Copenhagen researchers went back and analyzed the blood samples: 18 had the JAK2 variant; 14 of those 18 with the variant developed cancer in their lifetimes, and all 18 died within the study period. How, exactly, was this helping?
Finding that you carry a harmful genetic variant, and that there's nothing you can do about it, is probably the most frightening outcome when obtaining your personal genetic information. Some say they would rather not know about such genes.