This could be a PHP or HTML post.... I'm in internet marketing now and I was writing an SEO tool to pull info off google pages, and many of their class and id identifiers do not have quotes! like <div id=header> for example. This was wreaking havoc with my scraping tools. I used this php to fix it: preg_replace("/(class|id)=(\w+?)([> ])/",'$1="$2"$3',$body); Basically it fixes that problem. Maybe it is to discourage scraping?
What gives you the impression attribute values need to be quoted? While this is a SGML requirement, it's not required in HTML. Also, in the past, people complained Google didn't use a doctype but didn't realize that Google served their pages with proper http content-type headers so the doctype wasn't needed. From the W3C docs: I presume Google is using those "certain cases". A test case of a div using an id in the validator does not generate any error.