I chuckled when I saw the title of this article as I was working on a recursive CTE just last Friday and ran into circular references. I laughed out loud when I started to read the article as I, too, was working with Active Directory group memberships as well. FWIW, I came up with essentially the same techniques for dealing with it. I also plan to bring the circular relationships to the attention of our AD administrators and see if we can remove them somehow.

Thanks for the timely article.