Sorry about that Herb, I don't know how all my videos got set to private. Fixed it. http://youtu.be/uLlbuwJUg2U I wondered why I hadn't been getting any comments lately.
I don't tend to see robbing necessarily from the smaller ones, unless they get killed off while I'm not looking, which does occasionally happen in the summer. So there is some selective pressure there.
The one in the video has long been my strongest or at least top two hive. I have kept it with continuous unbroken lineage for ten years treatment-free. It was completely robbed out, not a drop of honey left in the hive. After the robbing was over and the robbers stopped coming back, I gave them a frame of honey, reduced the entrance to a single bee size and let them start rebuilding. That was two summers ago, and after being knocked over by a mobile trampoline this winter, they are still alive and were doing fine yesterday when I peeked in.
On a side note, I don't consider it the same hive if it has been requeened artificially.