And I think I know why this practice is used.
I believe most filmmakers want to set up a resonant image with their audience. An image which is both familiar and fictional. Audiences for TV news are comfortable with journalists as performers. The book "Breaking the News" addresses this very thoroughly. In fact the role is debated vigorously in listservs for journalists and TV news managers (who hire and fire them based on their "appeal" instead of their journalistic instinct).
Purely fictional appearances are usually agreed to because of the ego boost which comes from both audience recognition and wider exposure. Networks and services allow many of their "personalities" the flexibility to make these deals as long as they don't cast negative shadows across their own news organizations. The performers also get to hype their appearance to their own TV audiences as well as cross promote to "entertainment" magazine shows covering movies.
I remember how much I enjoyed seeing Louis Rukheyser (sp) of "Wall Street Week" being knocked to the street by Bette Midler in his "Big Business" cameo. What I also feel, when I see news personalities holding the "live" microphone and gesturing off screen, is the same familiarity I engender for the "stars" of the movie. It circles around the sense of "knowing" the person in a secondary role. The skills of performing a newscast are similar to a movie role except where movie roles get a whole lot more takes.
It's a different resonance when someone like Jane Fonda is playing a journalist. Here the familiar Jane is "performing" another familiar role and I find I am judging her on how well she interprets the "role" of journalist. When it's Bernard Shaw I'm judging his adaptation to the bigger scene (not necessarily the biggeer screen).
Many appearances by journalists are simply snap-shot cameo roles in support of a single scene. These scenes are rarely the critical to the story and are rarely responsible for conveying important information to the audience regarding characters or plot. The expection may be where Oliver Stone uses the machinery of media as a character in "Natural Born Killers". The use of a "journalist" as a central protagonist is particular to that story as it is for "Network" or "Broadcast News". But, then again, we're back to actors playing at being journalists.
Audience response to the appearance of familiar news personalities is much the same as the audience response to "look alike" actors who play cameo parts in TV commercials or promotions. It's resonating at a level of comfort and works to "frame" the fiction inside a familiar relationship already established in popular media.
Those journalists working in television who are focussed on being journalists and not performers would not "sell out" unless they were willing to give up their "credibility". The stock and trade of a "serious" journalist is their credibility. The stock and trade of a news personality is their "appeal". Contracts with newsmedia stars have come to include clauses on appearances in fictional roles and the sharing of revenue from those appearances with the organization they are affiliated with.
I wonder if anyone can think of a movie where a news personality (or journalist) appeared as someone other than their "professional self". Say, where Walter Cronkite plays the head of NASA, or something equally resonant. Like Francois Truffault appearing in "Encounters of the Third Kind".
Multimedia specialist and Web stylist for ATL
University of Alberta
"It ain't what we don't know that gives us trouble, it's what we know that ain't so."
‹ Artemus Ward
Online resources for film/TV studies may be found at ScreenSite