NTFS ACL Behaviour
If propagate from parent is checked
the original folder permissions will totally be replaced by the new parent settings.
example:
Directory c:tempjoe
permissions: joe RW , smith R
Copid to c:tempnew
already set permissions: joe R, smith RW, mark R
the files copied will be set with those permissions.
Same happens with any file that is put in that folders, they will
immediatly take the ACL of the current folder and lose previously ACLs.
ref.
http://technet.microsoft.com/en-us/library/cc783530%28WS.10%29.aspx
System Administrator