Michael Parson wrote:
> 1.  Backups.  Some of us still like to use dump/restore to backup our
> systems.  Dump only operates on partitions/slices, so we break things up
> to make those types of backups easier. / /var /usr /home /tmp, etc.

Having all base on a single partition certainly makes this easier.

> 2.  Stability and security.  If you set your system up right, you could
> mount / read-only and still be able to get work done.  If I keep /tmp,
> /var, and /usr off /,

> Filesystem    Size      Used     Avail Capacity  Mounted on
> /dev/wd0h     5.4G     1.3G      3.9G    24%    /usr/local

Seeing this example, I wonder what confuses you to assume that everything
under /usr has to live on the same partition. I never said, implied or dared
to put /tmp or /var on the root partition.

You did not show what's the difference between /bin and /usr/bin that makes
it worth to put it on a different partition.

There are very good reasons for placing certain files/directories on separate
partitions for individual reasons but such a layout is not used by default.
The default layout is too place certain files on a separate /usr partition
without any good reason or advantage as it seems.

-- 
Christian