I did wonder if it would be better if people could not merge information from other trees. If they had to enter each piece of information for themselves, at least it would slow them down a bit and they might actually read the rubbish they were adding to their trees and realise some of their mistakes. Well, maybe...
However, no doubt that might put some people off Ancestry and lose them custom.
How about if Ancestry can detect more than 100 duplicate individuals on your tree then it is automatically set to private until you sort it out?
I do so wish something could be done to improve the situation.