Maybe just maybe you meant to say "ancestry on line trees"?
I'm probably in the minority, but my genealogy research along with many other researchers have their trees uploaded to our own domains and have taken care to provide citations and references.
I am NOT saying they are perfect, as all manual entry methods result in errors, but there are some of us out there that do not necessarily condone all online data.
I do agree with the principle of this thread as there seems to be an explosion of trees on this site that contain impossible data... children born after the mother's death, mother's giving birth to children when they're in their 60s... and on and on. I leave comments when possible, but it seems like no one corrects anything and just keeps moving along to collect more ancestors.