Looking through Google's AdSense alternate ad specs gives yet another reason for yesterday's plain text node type. It also brings clarity to a portion of the need. The output needs to be served up, unfettered, but needs to include the ability to do PHP in generating the output. In the case of AdSense it would allow for various ads to replace the public service ads on a Drupal site if the author so desired.
Which brings me to the next item. For some reason Google has decided this page deserves only public service ads. Well not really but when accessing www.addingunderstanding.com it only gets public service ads. Go to addingunderstanding.com instead and the regular ads appear. Odd.