Rover flash.. Full?

The reports I've been reading on the state of the Spirit rover is that it simply filled up the filesystem on the flash memory, and that this was causing it to fail when booting.  (NASA mentions it briefly, here).

This seems like a pretty basic problem to me - something incredibly easy to predict and to avoid.  I hope there's more to this problem than what it sounds like, or it's some serious egg on the face of the folks in charge of the computing side of the rover.