Here's a fun academic study for you. A bunch of “political scientists” stick two groups of people in front of TV sets. One group gets to watch Bush and Kerry's 2004 Presidential campaign; the other gets to watch CBS Evening News's coverage of the campaign. They both then get to watch The Daily Show. The result? They both end up more cynical about politics.
What's the conclusion? Well, The Washington Post swiftly derives the following idea from the slightly iffy study: “Jon Stewart and his hit Comedy Central cable show may be poisoning democracy.
Now I could dwell on geeky things about the study that make it pants anyway, like why there wasn't a control group, how they managed to find people who hadn't seen the 2004 Presidential campaign and so on. But here's another interpretation: if you're shown videos of people saying things that appear quite nice (particularly since they've been through focus groups to ensure they sound nice), you're likely to give them a high approval rating; show them that these people are lying to you or saying things that are blatantly contradicted by things they said earlier and you're likely to get cynical and less likely to believe them in future.
In other words, maybe it's not the Daily Show that's making people cynical - maybe it's the politicians and the Daily Show is just exposing them.