Collapsed DMZ/Internal Infrastructure design

I have to agree with Jason, this is a policy discussion more than a technical one.  As he points out there are many ways to achieve traffic isolation. What a collapsed architecture does not do is provide fault domain isolation and that "line in the sand" of a network cable that seperates external, dmz, internal networks.   The other caveat is if you are in a regulated industry you need to account for your auditor and how they will consider a collapsed DMZ architecture.