Spam I Am
Having been condemned by every email filter known to man, I feel, for once, Google's pain. There was that one incident several years ago when a political twist, if you'll excuse the expression, made my name hot on the message boards. That I had obtained the name almost 50 years before made me a deity in smarmy political circles. Who knew 15 minutes of fame could be so long.
Keywords is a common but never official tag. The only official tag is title. The people who use the meta data sections of documents as well as the content sections, librarians, know that the official tag is subject (heading), but without a directed graph, subject itself is not quite right. However, a full text search never appealed to these folks anyway.
Rather than fuss about "keywords", the more interesting question, for Google and Microsoft is: Do you use, and how do you use "author", "editor", "printer", "creator" and "contributor" ?
And, while I'm at it, Google and Microsoft, the Personally Identifiable Information tags http://purl.org/pii/terms/ ? Sorry, shameless self-promotion, ignore that last question.