Hi Sue. I sympathise with your view and situation because, to some extent, 'lifting' names from some-one else's tree devalues the massive enterprise and effort (and sheer expense!!!!!!) some of us undertaken in order to get where we are.
I started out on Genes Reunited (ages ago) and was pretty excited, initially, especially when I found living family connections I hadn't known about. That has been a particular joy. Sadly, when ITV took GU over I saw things going down the pan and there was a huge furore about 'stolen trees'. I even came across one with over 220,000 names in it and was incandescant with rage when I noticed that my tree had been lifted wholesale, imported, and even a few significant names and dates changed slightly to make it fit. THAT was the moment when my tree went private!!!!!
I came across yet another living family member who had done some terrific research (and leg-work) and she introduced me to Ancestry. So I exported my gedcom, made my brother an editor (and we work together on it), and ensured that it was PRIVATE not public. As a precaution I deleted everything from the GU tree except myself with a silly name and rubbish dates and waited until this month for my sub to expire.
Why do I protect my tree this way? Well it is simple: I am a purist. I drive my brother to distraction because he is much more excitable than I and prone to flights of fancy. Generally, I allow nothing into my tree unless there are the required three pieces of primary evidence. Because our tree is verified in this way back to 1610 obviously there are some difficulties obtaining primary evidence for the earlier years but gravestones, newspaper reports, land taxes etc are all acceptable in my opinion. It doesn't just have to be certificates! Getting hold of such information has cost me a fortune and, of course, both of us now living well away from Northumberland we have to make expensive visits for periods to actively research various points.
Like many others I have the blinkers off and look sideways at my tree and this is because it fills out the picture and feeds my other main interest of social history. Quite often, the bloodline alone doesn't tell the whole story. If one comes across distant relatives in the process that is all part of the story. Three of mine are really 4th cousins once removed (two from the same branch, one from another) and their help has been invaluable. If it hadn't been for them I wouldn't have understood why some members of the family migrated away from the 'family seat' in Northumberland.
My view is simple: if one has information which needs protecting in any way make the tree private. You can always invite people in (even for a limited period). In Ancestry links still arise even if a tree is private. It just means the 'finder' has to approach the unknown owner for information. The control is then with the owner to decline or open it up. I am not interested in making a public show of what a wonderful job of work we have done (because we still feel we have only just scraped the surface) and I certainly don't want all the world to see some of our 'skeletons' we have unexpectedly uncovered.
This is only my way and I share it with you so you can see others face the same issues you have encountered. Sometimes there are decisions to be made and it would be better if some-one gave us guidance before we start because most of us just jump in with enthusiasm and then discover we have to unpick some bits!
David