You seem to be ignoring Cory Doctorow's main point: that other apps will be able to use the built-in DRM chip to ensure that even files created in 'open' formats will only be readable by that same app (or its brethren from the same manufacturer). Imagine if you created a plain text document in (say) Word and then the person you sent it to found it wouldn't open in anything except Word. I don't think anyone doubts (or worries) that the OS will be tied to the hardware, espec as that may be done in a variety of ways, of which TPM DRM is only one.
Macintosh: Intel Inside! Now Improved With Delicious DRM