As far as I can tell, Bob just assumes the IA comes first and hands off the responsibility for design to another, equally important designer (in his post the visual designer).
When I read Heather’s post, it seems she assumes the IA never really hands off responsibility, but delegates aspects of the design to other, less important, designers (I am exaggerating here to make a point).

As much as I dislike the waterfall method (I prefer a multi-disciplinary, iterative approach) I have even less respect for those who support the idea of the superiority of IAs.

As I wrote in my first description of the T-model for User Experience[1]:
‘Why would Information Architects be the ones to claim the “Big” label, effectively placing the related fields below IA instead of at its side. Do we posses a special skill that practitioners in the other fields don’t? What is that skill? Is it related to one of the deep subjects or one of the shallow subjects? I cannot tell and I think it is wrong.’

Heather writes: “Understanding the role of the information architect and inserting their expertise at the right stage of the Web design lifecycle is critical to the overall success in experience design.”.
And: “To create the best experience [..] requires well-organized structures, easily understood labels, and predictable placement for users to scan and select the next step in the process.”

All very true.
But the implication in both of your posts (and a little stronger in Heather’s) that IAs are somehow more important than other designers and hand off work to less important others is, IMHO, very wrong.

P.S.1: There is a small chance that I am misguided as to Heather’s intentions by the use of “Blueprint” in the title of her post. I realize that some people call the IA’s deliverable known as “wireframes” elsewhere a “blueprint”. If that is the *only* reason why that word is featured in the title, my comments are way too harsh
P.S.2: I’d love to hear what Bob thinks of all this!

[1] T-model: Big IA is now UX, http://www.peterboersma.com/blog/2004/11/t-model-big-ia-is-now-ux.html

In this case, I think Bob’s article emphasizes the importance of the IA role as the “architect” drafing the blueprint for the experience. The IA role can layout the structure, format, even (hierarchical) placement, navigation, etc. all to help influence and support the visual presentation of the experience overall.

The idea of having both competencies represented with the client at the same time is something we highly recommend and have found the best success with this process. We find having all creative stakeholders at the table brings forward the best, most holistic approach to creative discovery.

Equally, the client gets to see/ask/interact with a deeper bench of talent all at one time. Collaboratively, a creative team can build together instead of having a fragmented and disconnected group of specialists designing the experience from one “collector’s” point of view.

We did a follow up post on this article at: http://viaspire.blogs.com/weblog/2006/09/information_arc.html

Wouldn’t it be helpful to have visual designers gather their own requirements directly from the client, have them do the initial sketches (moodboard, visual language) and study branding guides before you go to work?

That way you can work side-by-side so that when you sketch your wireframes they think about layout and when you think about information hierarchy, they think about how to visualize it?