Someone must rid us of this meddlesome Google. They have way too much power over what gets seen on the internet. Today they're going after the broken links of people who post on your board - tomorrow they'll be telling you what usernames are ok.
This guideline is listed under Design & Content. A webmaster can choose not to follow any of the Design & Content and/or Technical guidelines without getting penalized. So IMO this is a non-issue.
Even if you choose not to implement any of these suggestions, we strongly encourage you to pay very close attention to the "Quality Guidelines," which outline some of the illicit practices that may lead to a site being removed entirely from the Google index or otherwise penalized.