Inadvertently coined by a writer for the Village Voice some years ago, in reference to Al Sharpton; it refers to someone who can't get enough of the cameras and microphones of the news media - the better to engage oneself in shameless self-promotion. Actors do this kind of thing to promote their film or TV show, and spin doctors do it on those talking-head shows, often in direct proportion to the lameness of the product they're promoting.