Interesting post but was really hoping to understand why some of my saves wouldn't transfer to other 360 consoles. Back when the "red ring of death" was more common, I would be issued a replacement console. When I snapped my hard drive back in and turned on Ninja Gaiden 2, I wouldn't be able to continue my progress. I had the unfortunate luck of this happening several times to me and I eventually quit playing that game.
Years and years later, I worked with someone who used to be at a gaming company and he claimed that apparently it was a quality assurance requirement from Microsoft in order to be published..