The short answer is that meta tags are no longer a requirement, and serve very little practical purpose in SEO. This is because they serve absolutely no role whatsoever in the ranking algorithms of Google or MSN, and play a very small part in the algorithm used by Yahoo.
This does not mean, however, that adding meta tags is completely useless. Even though it doesn’t count towards ranking, Google sometimes shows it to users on SERPs (search engine result pages).
Meta keywords are, if nothing else, a good organizational tool. I for one am a great believer in the value of sketching out lists of keywords and keyphrases that you want to optimize for, and keeping track of them on a page-by-page basis. So what better place to put them than on the page itself? This is an especially handy touch for plain HTML sites with no database, where you have to edit each page individually.
Despite the fact that meta tags are virtually obsolete for ranking, there is no doubt that they still have a few useful side benefits. Whether it is worth it to add these tags needs to be decided on a site-by-site basis, and largely depends on the amount of time involved.
As long as you use them in moderation, meta tags won’t damage your rankings. They won’t help them either, however, so if you are adding them to beef up your keyword density, you will almost certainly be disappointed.
