I received a 4th cousin hit today with the oddest result that I thought would be worth sharing with the group here:
When I opened the result (see screenshot), the only person displayed was the tested person "D. B.". No surname list whatsoever. To add to the oddness, the tree D.B. was attached to had more than 10 generations. I couldn't get over the oddness, and I had never seen anything here about such a result, so I called Ancestry DNA Help, thinking that this result was a software or programming glitch.
The upshot was: that "D. B." is probably the husband of the person who created the tree with more than 10 generations of HER ancestry. He has no tree whatsoever, except hers. Thus the result I received.