User blog comment:Godisme/Shades of the Bond/@comment-1752488-20111130175445/@comment-2048489-20111202161648

And what of how Hollow Ichigo and Zangetsu are one? Just playing devil's advocate here. Tosen demonstrated his Hollow powers to be an extension of his Zanpakuto powers by releasing his Resurreccion. I know he's an exception to the general rule, but it shows just how intertwined Inner Hollows and Zanpakuto are, especially Hollow Ichigo and Zangetsu. Plus, Hollow Ichigo is also Ichigo's darkest aspects--the Ichigo that would have existed if he had become a Hollow. He's a piece of Ichigo's soul. You can't take that sort of thing away. Just as Ichigo's Shinigami powers are part of who he is, so are his Hollow powers. In short, they ARE him. They are not "foreign" like Fullbrings are. Maybe I'm launching into a lot of speculation here, but Fullbrings, as the opposite of their hosts and bestowed upon their wielder by another source, can be traded around with more ease because they're BESTOWED powers. They're "acquired" powers. Not like Shinigami powers, which rise from within the soul of the wielder.

Meh, I'm probably speculating. Tell me off if you want.