Joe...a quick correction...
I'm not certain, but I believe the couplers on the Big Dipper are long U-shaped steel pieces which are captured together, but held apart by a large spring. My understanding (which may be wrong, mind you) is that the spring is what failed...the cars did not separate, but did bump together. Such a failure is extremely difficult to predict, and that spring could very well have been decades old.
It's not that Geauga Lake did anything wrong on Big Dipper; it's just that a part failed. And I should add that the seriousness of that incident was comparable to the seriousness of the Corkscrew chain incident at CP.
--Dave Althoff, Jr.