I understand and sympathize with the arguments for and against designers who can code. For me it boils down to question of what I to focus on honing.
I’ve noticed that people who are really good at design think entirely differently than people who are really good at programming; the two modes of thought are almost antithetical (that whole, left brain/right brain thing). I’d rather make myself good at one style, and let someone else be good at the other. There’s only one designer I know (probably because I don’t know that many people) who is both really good at design and can also code: Aza Raskin. Even still, when Panorama went from demo to prototype to production, every single line he touched had to be re-done. This is no criticism, being able to make a world-class prototype is a skill I wish that I, and more people, had.
Additionally, when people ask for “designers who can code” that’s not really what they want. What they want is a developer who can be be trusted not to turn out shitty looking UI. They want Ian Gilman, or Sean Dunn, a dev who understands the principles of design and UI, but is still a very good programmer. To me, a designer who can code is, ideally, someone who can mock up the interaction they want in a demo. Usually all you need for that is jQuery.
It’s not that I don’t agree that diversity of skill-set is desirable, I just think the argument is a disingenuous way to justify skimping on design. There aren’t enough developers to satisfy demand, so everyone is trying to get people with even similar domain knowledge (designers) to dive in and code as well. The article linked in the first paragraph might as well say that Silicon Valley is looking for janitors who can code. And yes, it’s been proven that software can ship without design, but it’s unclear, especially in the post iPhone world, if you can make money from that.