> Once more: root and /usr do not have to be separate file systems on the
> same spindle.  This currently exists in a default installation only
> because of a limitation of sysinst; they can reside in the same
> filesystem.  This virtually eliminates the loss that you are referring to.
> I don't know why this issue keeps coming up.

As I see it, whilst everyone has different requirements for their set-up
and so on, there is at least one good reason why you might want / and /usr
one different partitions.  

I, for one, have everyone's home directory under /usr/home.  This means,
since we don't enforce quotas, any user can fill up the /usr partition. 
Part of the boot sequence creates temporary files in /tmp (and whilst /tmp
is cleaned, if it were already empty, this wouldn't help) and would be
stuffed if the partition would full.  Thus rebooting with a full HD loses. 
Same applies for log messages and rotations, daemon pid files etc, etc.

Having key pieces on a separate partition can help to prevent annoying
little headaches like this, by ensuring that the system has a certain
amount of space to work in.

Just my 0.02ukp,
David Forbes.