pageoneresults - 11:57 am on May 14, 2011 (gmt 0)
You do not need the keywords element. Search engines don't use it.
According to Yahoo!, they still do and, they recommend its use in the Small Business Promotion documents.
What are meta tags?
Though the keywords tag isn't as important as it once was, effective keywords can still influence your search engine rankings. Your visitors won't see your keyword meta tags (which will be hidden in your site code), but search engines may use them to help index your site.
How should I write my keywords?
Maybe someone should tell Yahoo! that their documentation is outdated?