Cornish Jack:
The big difference between this incident and the 737 mishaps is that only half the rudder system failed on the 747 -- the remaining controls allowed the crew to keep the airplane under control. The fact that the airplane landed safely gives clear evidence that the split rudder system provides the redundancy required to guard against foreseeable failures.
As with any system failure that doesn't have a specific non-normal procedure addressing it, this one required the flight crew's knowledge of the airplane systems and the airplane's capabilities to successfully deal with the failure. In the 747 the rudder ratio changer (restricting rudder travel at cruise speed, but allowing full travel as airspeed decreased) would affect low-speed controllability as well as the general principle that control inputs are less effective with decreasing airspeed.
Since only a preliminary report was released, we don't know if the most significant cause is a design defect, maintenance failure, or a simple, unpredictable component failure. No need to go ballistic yet...