Rather than include the keywords in the meta tag of the HTML page, which is where information about the document is typically placed, VW was hiding search keywords inside the page. Using a div layer, which is a technique of building pages with style sheets, Volkswagen had loads of search terms that would register with web spiders, but not show up to end users. The end result would be the Volkswagen pages would be called up for more searches on Google than they otherwise would be.
The name of this suspect layer, "invisibleContent," seems to clearly register its intent. Since being flagged, Google and Volkswagen's agency had a chat, and the search terms are now properly placed under the Meta description in the page. Oh yeah, the pages now block web crawlers from caching the pages - a total 180 degree turn from spamming search engines with hidden terms. Very weird.
Some webmasters are a little miffed that Google didn't throw the book at VW and kick it from the search engine's index, a particularly devastating reaction for websites that Google often has when a site is found to be violating its quality guidelines. Apparently it doesn't matter, however, since VW's blocked its site from being cached anyway.