In a case that has stirred up quite a buzz in the law enforcement, legal, unsolved mystery, AND genealogy communities, a serial killer was recently arrested due to his DNA from the victims being matched with a close relative of the killer's on a DNA genealogy website.
I'm not sure why people didn't see this coming as DNA matching on genealogy DNA sites has been used for the past decade or so by adoptees looking for biological relatives. And previous to this case, the DNA services have been served with warrants looking for specific matches. In other words, if you are a criminal and have left DNA behind, your days of being a nameless, faceless suspect on the run are probably numbered.
While people may rant about privacy, whether in regards to DNA, online information, stuff posted on social media, etc., the fact is, when your information gets out to the public, it is out to the public forever one way or the other. And now with so many people submitting DNA to these services (remember all of those ads on TV right around the holidays to "find your roots" with a cheap DNA test?), the possibility of matching even more suspect DNA is increasing every day.
Interestingly, it wasn't the DNA testing company that provided the match information to the police. No warrant was needed since the person who submitted their DNA posted it on a public "bulletin board" of sorts looking for genetic relatives; this is a service that anyone can access. The tricky part is that while a person is sharing their own DNA information, the fact that their DNA isn't exclusively theirs (parts of their DNA are shared with relative from close--parent or sibling--to quite distant--fourth cousins and such) makes things like personal privacy more difficult (impossible?) to manage.
I don't even think this is the tip of the iceberg as far as DNA is concerned. I'm sure health insurance companies would love to use DNA as a way to eliminate high risk applicants from insurance pools. And mental illnesses can be found in DNA so there is always the possibility of preemptively targeting these people for everything from gun use restrictions to barring them from certain jobs. Cloning isn't even outside the realm of possibility with all of this readily available DNA.
How can you protect yourself from the future threat of your DNA being used against you? I don't think this is possible. If someone really wants your DNA, they can get it. And if they can't get it from you they can get close enough from a relative.
The mind boggles at the future repercussions of this.