I did the ancestry.com DNA test because my mother-in-law paid for it and I wanted to trace my Cherokee ancestry. I didn’t really consider the security ramifications at the time. The truth is there have already been court cases where the government has subpoena’d the DNA results to identify potential felons. There are definite security risks associated with the tests.
Ancestry has a policy to release it to any government agency with a valid subpoena.
If you don’t want your DNA in the “system” don’t ever provide it. Mine was already available since the USAF collects it on ALL service members for use should you die in combat and are unidentifiable by other means. It is pretty easy to collect it, too if you really want it. Pick up a used coke can, coffee cup or even a hair from a comb and submit it to a DNA lab. Once you dispose of the cup I don’t think you have any rights to the DNA on the cup.
As a result of submitting my DNA to Ancestry.com though I’ve discovered numerous relatives I previously had no knowledge of including a baby that was put up for adoption which no one in the family had previously disclosed. I have a great aunt I didn’t even know I had thanks to Ancestry.com.