Thank you for this. If I had an 11th Pet Peeve, I'd add your article to it. In fact, I may. http://1hx.blogspot.com/2009/12/web-usability-top-10-peeves.html. I will be pointing people to this post frequently, I'm sure. We have many people in our organization who think that because they use systems (in general) they are qualified to design them for others. For those, we try to at least convince them to let us do testing and design validation as we would do for our own designs.
thinkpink is a weblog by Elliott Kember.
He is on Twitter: