I recall an article (by a Google employee) that says keywords are obsolete now regarding SEO. This may be true, but is it possible that meta keywords can determine relevancy of AdSense ads? Another words, should meta keywords be ignored or used?
Google "says" they're not relevant anymore but I still use them. The least it will do is let the spiders know what the content is about. Weather or not it helps in SEO really doesn't matter. It takes about 5 mins max to implement on your site. Why not do it, is the question.