Most of the family trees I have were built using a persons Ancestry DNA matches for the purpose of ferreting out biological families. AncestryDNA provides a road map and Ancestry.com provides a lot of data. And from there you can substantiate links further by using public sources like Newpapers.com Linkedin, FB, Spokeo, MyLife and Whitepages. When dealing with adult adoptees or a adults from a single parent home the results must be 100% accurate and you must be able to explain in detail how all the pieces in the puzzle fit to together for this result. And it can take 2 days to 2 years to reach the conclusion. I've done that for 20-30 people with a 100% success rate.
One of my GGG-Grandfathers was a Robert Henry with a unique surname who was from Ohio and later moved to Missouri. I found another person with the exact same name who was married in Kansas City, MO in the late 1800's. Same guy? Maybe a son? Maybe related? A lot of family trees had this as the same person which ended up not being the case. The Robert Henry married in KCMO was a cousin and he had quite a interesting life. His parents died when he was young. He lived with an uncle for a short time, then set out on his own around the age of 16 and really made something of himself.
GGG-Grandpa was a real character, he got a field commission after Vicksburg from a Sergeant to a 1st Lieutenant, he apparently abandon his first wife and child in Ohio, married a woman in Missouri whom he had 10 kids with, his Civil War pension was declined because there was no record of a divorce from the first wife.....and likely why he is not buried near his 2nd wife and sons. On Christmas Eve 1868 someone embedded a drawing knife 1-1/2" into his skull, from that point on he was severely ill and he finally died in 1885. From 1868-1885 despite his debilitated state he produced 8 of his 10 children, the last being born in 1885
A little leg work goes a long way and will separate you from the chaff. When people find your tree of interest they will in turn populate Ancestry, MyHeritage, etc with the data you provided and in time that will over write the crap.