i get the idea behind this meme. i do. sites that are pretty instead of functional are self serving, and only confusing and disenfranchising to their users. i think that there should be a push in the design community to consider how the underlying HTML of your site works, without all the images, CSS, and other prettifying parts of the website.
CSS Naked day tries to do this by showing everyone the equivalent of View > Page Style > No Style (in firefox). Functionally, it reverts websites back to (almost) text only days. This is a great way to show designers what's wrong with their sites. despite the fact that everyone who participates having to put up massive banners to explain to their users what's going on, before they assume the site is 'broken'.
self serving, confusing and disenfranchising to users, stop me when this sounds familiar.
that's why my site kept up appearances all day yesterday, despite my position as a designer.