Many people who submit their DNA to a direct-to-consumer company also upload their raw information to public databases like GEDmatch, which law enforcement can access. People upload their raw DNA data after taking another test, like those from 23andMe or Ancestry, to several open online DNA databases. Most companies do not release database information to law enforcement. However, a recent study found that, using publicly available data, it's possible to identify up to 60 percent of Americans with European heritage via third-cousin-or-closer DNA.
All this comes into sharp focus with the comprehensive kits such as the one provided by 23andMe: the one I drool into a tube for (incidentally, 23andMe doesn’t test for Huntington’s disease). Most people, like myself, have a low understanding of genetic variants, what phrases such as “higher risk” or “probability” actually mean or how to interpret our results correctly. Is it right that ordinary members of the public must navigate potentially frightening and/or misleading results alone?
Even the cousin matches seem to be based on the surnames listed in your tree with no attempt at comparing the people between trees to see if there is actually anyone in common! I have managed to find a few actual matches in the cousin match list, no thanks to their matching service, but more to the fact that I have been researching my tree for many years and am fortunate to know someone who is very competent at DNA and family tree research to help me weed out the rubbish from the genuine matches.
More controversially, some of these kits profess to tell you your biological (as opposed to actual age) by measuring the length of your telomeres (in basic terms, the caps at the end of each strand of DNA that protect chromosomes, like plastic tips at the end of shoelaces). Other tests, such as 23andMe, predict higher risks of developing serious conditions, such as multiple sclerosis, Alzheimer’s and Parkinson’s, including the test for BRCA1/BRCA2 (breast and ovarian cancer) that Angelina Jolie famously underwent, going on to have a preventative double mastectomy and surgery to remove her ovaries.