Actually, I use disktab(5) files to document the size, geometry and 
partitioning of the drives I install on various systems.  I have a master
file which I ammend everytime I get a new drive that I want to use with
NetBSD.  this allows me to document drive partitions in one central place,
as well as restore labels that get corrupted by errant writes.  It's also
useful for drives that are used in raid configurations.  If I use the same
label on all drives in the raid, I can be sure that as drives where out and
are replaced, I don't have to worry about going back and reinventing the
wheel with respect to the partitioning and/or geometry.  It may be that
there is no need to keep a central disktab(5) database which is distributed
with the NetBSD software, but to say that disktab(5) is useless and that
its functionality serves no purpose is completely missing the point for
potential large institutions which might have numerous instances of a given
drive type/partitioning scheme.
-Brian