Today I was demonstrating to a client how to create a "wiki" of sorts on their site. But, I had to sternly tell them that they need to figure out the hierarchy first, because they won't be able to rearrange the "parent/child" relationship after they create the page (unless they FTP into the site to move the files around physically).
It would be great if they could drag files within a tree on the backend. There are probably a lot of repercussions. What if they drag the page into a protected directory or a folder that declares a different _template or _layout?
But, drag and drop is the most natural way for people to interact with files. So it's something to consider.