I was wondering if anyone uses ACLs?  I can't understand why they are necessary since regular file permissions seem to do the same thing, plus there are other alternatives such as selinux.  Is it safe to say that ACL's are not very popular? 

Another question is why the chattr command even exists, since only 3 of its options even work with newer filesystems now, what use is setting the (i) attribute compared to chmod 400?