UPDATE: After receiving numerous comments from people interested in crucifying me for this post, I'd like to make it clear that everything below is in reference to your Web site ranking on the Internet; not on an Intranet. If you're constructing an internal site, by all means, use the meta keywords tag since it is utilized by many intranet platforms/engines. But as far as ranking on the Internet goes, it's useless.
Back in the butter days of SEO (Search Engine Optimization), the meta keywords tag was a sure-fire way to ranking success. All you had to do was stuff that bad boy full of your keywords (even using the same ones multiple times for added effect) and you were GOLDEN! But now in 2010-going-on-2011, those days are long-gone. These days, the meta keywords tag is totally and utterly useless to your Web site... or is it? Here are 10 reasons you may want to actually consider using the meta keywords tag for your Web pages:
1 - You truly believe it's going to help you rank even though every industry pro tells you otherwise. You've got something to prove and by golly, you're going to prove it!
2 - You want to waste your time. No, seriously... You really do want to just completely and utterly waste. your. time.
3 - You want to give your competition your BEST and most researched keywords on a silver platter!
4 - Facebook and Twitter are both down at the moment.
6 - You hacked Google and uploaded an undetectable virus that completely switches their page rank algorithm with a "meta keywords" algorithm. You're golden here, because you're the only one who would actually be using the meta keywords tag these days! SELF HIGH-FIVE!
7 - You want to populate your <HEAD></HEAD> section with every possible meta tag known to man.
8 - Because you're a TRUE SEO guru who practices what they preach!
9 - You've figured out how to travel back in time, yet somehow keep your Web site intact and on the Internet when you get there. (On a serious note, if anyone actually figures out how to do this, please shoot me an email.).
10 - Because you can, dang it! And not Google or Bing or anyone else can take that away from you! HA!
Key Takeaway: Please don't use the meta keywords tag. There really are no good reasons to where ranking is concerned. That is all.