Hmm, so they buy it from multiple vendors rather than use one specific model? That's a bit of a pain since there are significant reliability and performance differences between models.
I've owned macs since the Mac SE/30 days and (knocks on wood) never had any issues. I think for the most part, most HDs are nearly the same quality wise. I think seagate may be the only exception, as many people have complained about their products recently.