I've noticed some media organizations (NY Times, Washington Post, etc.) purchasing keyword ads from Google, Yahoo, and other services for a long time. A new article in The Wall Street Journal article: News Sites Turn to Advertisements On Google, Yahoo to Boost Traffic (reg required), takes a look.
News organizations don't appear to be adopting the strategy in large numbers -- at least not yet. "If you're in the online news business, ultimately your goal is to draw eyeballs to your news pages," said Robert Niles, editor of the University of Southern California's Online Journalism Review. News sites "need to become more aggressive in trying to [draw readers] to all the great content that is buried on their Web sites." He believes more sites will use the ads.