A long time ago in a land far, far away...
I learned, much as Tim learned, that when you have a working system that isn't quite as it should be, it was probably brought to working order by someone that knew what they were doing and left it that way because the proper implementation caused a problem and nobody wanted to pay to bring it up to snuff. Although, there should have been a pair of 6500s at the core. Who the heck built a network that uses 6500s and doesn't deploy pairs them in a redundant fail-over configuration. They don't even mention carrier redundancy.