SkyDrive seems to be religiously repeating some of Windows early mistakes by privileging easy of use over privacy and security.
Is respect to privacy, SkyDrive default option to announce on messenger all the new public uploads is just as hard to explain as when Windows used to start unnecessary services just because they could ever be used! When people upload public files, they sometimes expect this publishing to get unnoticed. SkyDrive just defaults to announce it for you. A couple of friends had some problems with this unexpected announcement and they finally unchecked this option. So did I.
In regard to security, things aren’t much better. One of my friends closed this public folder and asked me if I could still get to his file. And I still had access. Why? Because I had the folder page opened, where the document link stood. It seems like all you need is the link itself, after that you won’t be needing authorization – not even authentication!…
Oh well.. at least it is free :)