When companies like Ancestry.com and 23andMe first invited people to send in their DNA for genealogy tracing and medical diagnostic tests, privacy advocates warned about the creation of giant genetic databases that might one day be used against participants by law enforcement. DNA, after all, can be a key to solving crimes. It “has serious information about you and your family,” genetic privacy advocate Jeremy Gruber told me back in 2010 when such services were just getting popular.