Google does not use the “keywords” meta tag in its web search ranking. Google’s Matt Cutts explains this in a Webmaster Central video. This is not breaking news, by any means, but there are a lot of people out there that still put a lot of stock into this.
In fact, Cutts mentions that people have sued each other for meta tag keyword theft, when really this is just a waste of everybody’s time, because they don’t even play a role in the ranking of sites on Google.