Ancestry may have an algorithm for blocking access to “living people”, however, it does not take a great deal of effort (or skill) to identify them and gather a lot of information about them. I keep my trees on Ancestry private, but searchable
so if anyone needs information from my tree it is necessary to contact me for it. My trees are also private in response to requests from other family members to protect as much as possible the information available about them online whilst still being able
to continue my research. My Heritage is not the only service provider to offer all kinds of inducements, though, to putting and keeping your tree online, and although some may be worthwhile, the benefits need to be assessed clinically before you get tempted.
As far as finding my information on other peoples’ trees, that problem is endemic. The failure to respond to notifications when you discover an error is unforgiveable, but sadly is the case the majority of times. Eventually, errors spread
so widely it is all but impossible to get corrections out there. Keeping a tree private does, at least, allow you to control who has access to your research, and keep them up to date with developments.
I think I might have a tree from years ago on MyHeritage. I will check and delete it.