On my systems /usr and /usr/local are always mounted
read/only, like they were meant to be.
The problem is that when I try to install an rpm, it may
do an incomplete install, but especially if I remove an
existing rpm, it will be removed from the database without
its files being removed from /usr.

So far, I've worked around this problem by moving
/var/lib/rpm to /usr/lib/rhs/rpm, which prevents rpm from
getting a lock on the dabase if /usr is mounted read only,
but it'd be much better if RPM checked if it has write
permissions before doing anything, and abort right away,
instead of doing half the job and bailing out later