I'm afraid half of the contributors to this post believe that the task of the public tree is to help them with extra information while others wouldn't need their collected knowledge. I find this to be a very selfish attitude. The public tree is a surface of exchange, where I pay with my collected data for other's data. In this exchange, it is natural to leave living people's data hidden, but less fair to make all old data private while expecting help from others (or why are you in a public space?).
There is no sense to speak about 'my tree' on a public surface. Especially I also collect similar family names from neighboring villages and also add their sources if they appear. These small trees are not connected (yet) to 'my tree' but I hope to find once the common ancestor. Sometimes these small trees hit another existing tree -- in such a case I added a few people to the tree of a potential relative. If we find a common ancestor the whole chain becomes 'my tree'? Or his/her tree? Has it any meaning?
To build trees from records is a kind of voluntary activity. To faith against such people is similar to as if you'd fight against people who take photos in 'your cemetery' and 'your graves'. At the same time, I understand the expectation that such voluntary activity needs precaution, and I myself dislike those people too who connect families too easily, just because they could be relatives. But in such a big group, it is necessary to accept that you can't prescribe to other people how to behave. First of all, if you'd not like other people to prescribe your behavior.