Although it's not likely, it can happen that a driver blows and goes open circuit. If this happens, the results will be different according to how the cab is wired.
If two drivers are in series, connected in parallel to two other drivers in series, you finish up with a 16 ohm 2 speaker cab.
If two drivers are in parallel, connected in series to another two drivers in parallel, you finish up with a 12 ohm 3 speaker cab.
At first glance, the second option may seem better. However, the single speaker will have to handle four times the power that each of the drivers in the pair do, which may well result on it crying enough too, so you finish up with an infinite ohms cab.