Sorry, it's one of those vague body shots. If you have a monoqoque frame, you don't even have this bit. It is the area right around the seat quick release lever on the old style frame.
I think that they did away with this on newer frames to better accommodate the rear folding rack. But it is the most effective seat post holder upper out there.
I do not think that anyone else would ever develop such a crack. It's not at a stress point on the frame and is not in any way dangerous. I'm going to keep riding until it cracks all the way through.