Question:

Under what circumstances might some of the normals on a poly model become reversed?

I've read discussions about fixing normals that get reversed and I don't understand. It seams that for some people, a few normals here and there are becoming reversed. Not the whole model, only some of the normals. I've never had this happen and I don't understand how it could happen. I understand about reversing ALL normals to face either in or out but the idea of random normals flipping puzzles me. Can anyone explain some reason's why this might happen?