In my case someone had to find a birth for a david brunton, around the 1760s. They found a birth certificate, this happily had the "correct" fathers name, and this linked up merrily with all the preconceived ideas they had.
Unfortunately, they failed to take into account Davids death certificate the next year, Davids "father" actually died as a child himself, and the actual father was a different line of Bruntons from the same town.
Chinese whispers ensued, and the absurb became "fact" - not helped in any way by the blind assumption that the ancestry website is gospel.
Sure I'm distantly related to Shakespeare, William the Conquerer and Joe from the chip shop myself, as are most of us.