Well this is my story:
We [my wife and I] have been married for 48 years [I am now 73] and we never had kids.
Four years ago [late December] my sister bought a Ancestry DNA kit to try and find out more about our grandmother born in the 1880's, as our grandmother's father was unknown and thus a missing link. There were family rumors but nothing could be proved, because the man in question's two children died without issue, therefore as it turns out there is no close DNA available. [She was hoping to find out for her children's sake and to make it easier to keep up the family history. I of course had no need]
Anyway at the very same time [four years ago] a 47 year old lady in Sydney received a DNA kit for Christmas from her daughter, as all her life she yearned to know who her father was, because her mother wouldn't say or couldn't say!
A couple of months later when both peoples DNA went into the system you could say that the system bingo, or match up. Both parties received notification that they were only 1 degree separated and both wondered how could that be!
The lady in Sydney found my sister on Facebook and contacted her asking how is this possible, do you have any ideas?
After a few backwards and forwards emails they concluded that someone close to my sister could be her missing father, and that someone could only be either my father [who would have been too old] or me!
Can you imagine how I felt?
I was asked if I would do a paternity test which I agreed to immediately, as I wanted to know one way or the other too.
Once I started talking to the lady, got photo's, found out where she was born, I was certain that the DNA from Ancestry wasn't wrong and so it was proven 4 weeks later by the paternity test!
Fast forward today. I now have a daughter [now] 51 years, three grand children and four great-grandchildren, the last one born 14 days ago.
Buying those two Ancestry DNA kits has made two people very happy and all of the families surrounding them.
Mine is a good story, many more will be the opposite for some people.
P.S. On the very first day that my sister contacted me, my immediate reaction was to buy my own kit and use it. When it arrived my wife said, "you are not using that, I don't want anymore children coming out of the woodwork", so I never did use it.
Instead I tried to give it to three of my best mates and they all refused to take it - I wonder why?
In the end I did give it away and in a short time it solved another 50 year mystery, and made someone else very very happy. I don't want to say anymore because of privacy, but let me assure you in my experience the kits could not be more accurate!