Bing has confirmed that they still look at the meta keywords tag when crawling sites but instead of using the information as a ranking signal, the search engine uses it as a way of detecting spam.
The meta keywords tag dates back to the early days of search and it was meant to help engines and crawlers classify content on pages. However it became antiquated due to the level of abuse by spammers looking to rank for as many terms as possible. The tag is largely ignored by engines and SEO professionals but is still used by many spam sites and those with a poor understanding of search engine optimization.
Bing is advising that sites using Meta Keywords don’t need to remove the tag so long as it is following best practices (which I believe to be 5 to 7 keywords at the most). However if your site is using more than that or you’ve been advised to put as many phrases as possible into the tag, you may want to remove it.
As far as how Google views the meta keywords tag, the search engine does not use it as one of their ranking signals.