Update: New story named Yahoo's Senior Director of Search Got It Wrong, Yahoo Uses Meta Keywords Still.
It is official, no major search engines use the meta keywords tag for ranking purposes in their search algorithms. Yahoo's, matter of fact, announcement of this on Tuesday during the Ask The Search Engines: Best Practices Edition at SMX East conference was a bit of a shock.
For a long time, the industry some what made fun of Yahoo for using it (at all) for ranking purposes. Then, during the Q&A period of the session, Cris Pierry, Senior Director, Search, Yahoo said at 2:09pm (EST), that they no longer use the meta keywords tag for rankings. In fact, Yahoo stopped using it a "few months ago," said Pierry.
I was a bit taken back, and so was Danny Sullivan. Danny asked Cris, why didn't Yahoo announce this? Cris basically shrug his shoulders. I then asked Cris, "are you sure?" Cris gave me a look, the look like, that was a dumb question, since he is the man now behind Yahoo Search.
So there you have it, you can now stop wasting your time with it cause Yahoo doesn't even use it. Oh, well, if you use Yahoo paid inclusion or use a custom search feature, you may want to continue to use it, but outside of that - no need.
Forum discussion at WebmasterWorld.