The recent devaluation of meta keywords by google has changed my view entirely on meta keywords. A monopoly on Internet Marketing is the last thing we need. At this point they are not even needed and will make very little impact on your site. However, maintaining your integrity while choosing them is always a must. The last thing you want is your new site that you have worked so hard on to be flagged for something so silly. As I said before this business is about survival. The crawlers are getting smarter everyday so we must adapt with them. However when choosing your keywords remember to always choose relevant keywords and never use the same keywords for each page of your site.
Yahoo on the other hand still uses meta keywords, but if anybody has been paying attention to the stock market recently the future for yahoo doesn't look so bright. Google is growing everyday. This is bad for Internet Marketers because Yahoo is the only company left competeting against google and we all know competition is good for everybody. This isn't 2001 anymore and crawlers aren't relying 90% on keywords anymore.