... Even if the USB stick is not mounted. Run cfdisk, partition it, save the changes, and suddenly the volume manager and power applet stop working, and htop shows that HAL is not running.
In older versions of HAL, the behavior was for the volume manager to show the old partition layout until the stick was removed and plugged in again - obviously not the best outcome, but much more reasonable than just crashing.
Again, FWIW, this applies only to partitioning the USB drive when it is not mounted. Partitioning while it was mounted would be pretty much guaranteed to cause problems, but IMO partitioning an unmounted USB drive should not crash anything.