ChrisN,
Thanks, I didn't notice the diagram link before.
This confirms in my mind that the main reason for the accident was the two aircraft were flying "opposite" patterns.
At controlled fields, there will often be left/right base leg aircraft controlled by ATC. When I have been in that situation, the controller will repeatedly call traffic, and confirm that the pilots have each other in sight.
At an uncontrolled field, pilots really need to know what the circuit procedures are, and follow them.
If I were to lose sight of conflicting traffic, and couldn't resolve it quickly via RT, I would be leave the circuit, climbing above circuit height, then re-enter when I could determine where everyone was.
Most mid-airs do occur in VMC in the circuit, and pilots need to very aware of what is going on at all times.
Mike