I have to admit to putting a tree up on ancestry using the research of others. I have kept it private though, only inviting those that have contributed to see it. I was under the impression that you wouldn't see the details of anyone who is still living, and having done a quick search I don't appear to be there! Only scrolled through a 1000 names though

The research that has been done by others has been added to my tree with their full knowledge and I wouldn't dream of making it public without their consent. Also they have added stuff to their trees that I have done.
As mentioned in my post in the main Common Room forum if it hadn't of been for making a discovery through a simple google search I would still be pulling my hair out. This work, submitted on a webpage by a distant cousin was prayer answered. I do though always check everything myself, make sure that I have the correct sources and still have issues with everything that's on the page (for the life of me I can't find where they got some of their information from

).
I suppose it depends on how proprietary you are with the information gathered and your reasons for doing genealogy. I have no qualms about sharing my information but can see why some people would get upset at having their work shown. Perhaps there might be a copyright issue, I'm not a lawyer, and you should be duly referenced like any other author would be in a written, quoted work. I do notice that with the recent changes on ancestry you are able to write a little introductory piece on your submitted tree, an ideal opportunity to reference others.