Mattcutt clarifies that Google does't use keywords meta tag in webs search, i saw a video regarding this. Well he also clarifies the importance of meta description on your web page.. See Mattcutts video here.. http://emergingseo.blogspot.com/2009/09/mattcut-on-google-doesnt-use-keywords.html
i have already noticed this news from other blogs, he also pointed that the meat description is not counted for ranking, there is total more than 200 sources for the SERPs.