The Golden State killer, who is suspected of 50 rapes and 12 murders between 1976-1986, was arrested this past week. He evaded police for over 42 years and is 72 now.
If the information posted by the news is accurate, one of the suspect's relatives sent his DNA into either Ancestry.com, 23andMe or another company to receive a DNA analysis of their heritage.
One of the options you are offered when activating the sample is whether or not you want to allow searches for matches between yourself and other participants to possibly identify and reunite missing or unknown relatives.
The DNA data sent to the primary testing site is private. However, when you opt in for the relative search database, no privacy is provided. You're opening yourself up to other relatives finding out who and where you are and they are doing the same.
The Cops ran DNA samples from some of the crimes against that third-party locator database, and they got a hit on a relative of a possible suspect. Through family tree information, they developed a new list of potential suspects.
The police then obtained warrantless DNA evidence from each potential suspect, such as DNA lifted off doorknobs, discarded tissues, cups from trash, etc. One suspect's DNA matched most of the 12 DNA samples from the murders.
So, the implications for this case are pretty clear. One major issue is whether someone submitting a DNA sample to a heritage-finding service can legally opt-in and waive privacy rights for all family members. While that DNA sample is specific to the submitter, it also contains markers for all close blood relatives. Without knowing it, you could be giving law enforcement, medical insurers, and others a stepping stone into the DNA background of everyone with whom you share your DNA.
For anyone still interested, Ancestry.com is offering a $20 discount for new customers right now.

P.S. The suspected killer/rapist was once a police officer between 1973-1976.
http://www.dailymail.co.uk/news/article-5663349/DNA-genealogical-site-caught-Golden-State-Killer.html