Well, it pretty much lost much of its credibility when Bush and the rest of the rats made a case of invading Iraq and NOT ONE American media outfit bothered to check the facts. NOT ONE!!!!
Not only that, although I am devoid of any proof, I am certain that there was a clear cut intent by the part of the media as a whole to quiet down opposing "official" rethoric. Once example is that guy Wilson and the spy-wife of his bringin up reports stating that what Bush had said in the Sate of the Union was a lie... And not a single channel gave the story any credibility.
Powell and Friends go to the UN, an organization they detest because it represents international consensus, with a bunch of pictures of a square building and the drawings of a truck supposedly driving around Baghdad and concocting WMDs and noone said SHIT. I vividly recall The Jew York Times calling the theatrical piece "A Slam Dunk!".
Now, it is understandable that the US media might've missed the story, but it was all over the foreign press. I'm pretty sure NYT's people were reading BBC.com, El Mundo, Le Figaro, etc.
Whereas the media from the rest of the world was calling for diplomatic accords, mediation, talks, etc; the US media was SHAMELESSLY laying the groundwork for the Bushies and their kill-a-milliathon.
Needless to say, I no longer read the NYT, I wipe my ass with it. Nowadays I'd rather read a foreign (British, French or Spanish) newspaper rather than wasting my time in governmental propaganda.
I'm not saying that all US media is bad, I'm saying it is bad when the US government wants it to misinform the Flock of the Ones to be Led.