It sounded to me like Don Norman had already accepted that idea to the point that he didn't even realize it was a choice. He worries about a future of greedy carriers controlling our phone-brains. I worry about the fact that our minds could become so beholden to devices that, regardless of whether those devices are open or privately controlled, we diminish the depth of our experience and our tendencies towards reflective thought.
If drugs were available that increased our abilities but made us less thoughtful, would you accept that without deliberation? Would it really be better if those drugs were easy to make at home or handed out for free rather than sold in stores? This is already happening with Ritalin and "smart drugs". They improve our ability to carry out mental work but diminish our ability to reflect on what we are doing.
"Smart" drugs and phones are only so in terms of instrumental reason, not in terms of creativity or contemplation of ends.
No. It is natural and true. Intelligence Augmentation is already there, in the form of the internet and our array of portable computers, which give us access to any information or computation we know how to find or express. We are already some distance to Stross's Manfred Macx (from his novel Accelerando) - lost and slightly bemused when disconnected from our external brain. It's not so obvious yet, and most of us still have some independence, but those of us who know how to use the web are lesser people without access to it.