This tag used to get a ton of play for SEO, but is now largely ignored by the search engines. I believe it fell out of favour due to manipulation and misuse. It is a tag that is not seen by the end-user, so unscrupulous web masters abused it and it became less-and-less important for SEO. Real SEO tactics don’t abuse or deceive. I still populate my keyword tags because I believe they are still looked at, but I don’t believe they are very critical. If nothing else, it’s another instance of your keywords. They all help SEO.