Exactly. I have an obsession with "optimized" markup, that means avoiding unnecessary elements, ids and classes. Let's not forget that all this stuff sits in markup and gets downloaded on each request. Even if that does not add up to much, I still want to have my code "clean". There is one particular site that inspires me: http://camendesign.com/ — take a look, not a single id or class.
He did this, however, at the expense of convoluted selectors, pseudo-elements, and pattern matching. Personally, I don't find his implementation to be very clean. I guess it's better to have the mess in your closet than wide out in the open, though.