So I guess Lori stepped back?

I can write something about it, but you could also check out this first; http://sqlblog.com/blogs/hugo_kornelis/archive/2007/03/29/can-you-trust-your-constraints.aspx

(The blog post itself uses a check constraint to illustrate the issues, but an example that uses a foreign key can be found in the comments).

If you want an article specific about untrusted FKs, I'll write something up for you. Just let me know.