From the TaxProfBlog:
Lee A. Sheppard has published Shelter Penalties: Or Else What? Part 3, also available on the Tax Analysts web site as Doc 2005-3055, 2005 TNT 30-5.
The article in Q & A format reports on a session of the ABA Section of Taxation meeting in San Diego on January 22 where the authors of Circular 230 answered questions about it.
More about Circular 230 here.