I can be usefull when for example you want to allow the computer writing .tmp file on c:\ partition, but restrict the user (with only user rights) not writing his documents there. We can't do that with acl's I think. I don't want to schedule a file deletion, but a restriction of writing there. For example I don't want them to save downloaded virused .exe files in their documents zone, but they would be able to save their .doc , xls, pdf....., would be some kind of security..... another example, I have to let write access to c:\ for administrative working tasks, but when I let them write there, they polluate the computer with their files, and it is very hard to save their data from a computer to another...