I think another important aspect of this is that the (relatively unchanging) resource at /2012/01/02/news/ shouldn't be moved to /archive/2012/01/02/news/ witho

I think another important aspect of this is that the (relatively unchanging) resource at /2012/01/02/news/ shouldn't be moved to /archive/2012/01/02/news/ without at least a redirect. The point being that if the resource still exists, the old URI would preferably still point to it. If you, as the arbiter of the resource, decide to remove it, of course the URI will break.