Unlinked layer masks no longer get resized in an image resize operation – nor do they respect canvas size changes (ie. if you add canvas to the left side of the image the mask does not stay to the right with the rest of the image) . This is really painful – manually turning back on linking in a big document just to do an image or canvas size is a pretty awful workflow – and there's an enormously high risk of not spotting the error created from an unlinked mask until its too late.