Finally, someone in the mainstream media has evaluated in a public forum the truth about Fox News Network. http://www.washingtonpost.com/wp-dyn/content/article/2010/03/11/AR2010031102523.html
Journalism has as its basis the verification of facts; otherwise, it is propaganda. I could list a page of untruths that Fox has allowed to suffuse its evening "opinion" shows (when most Americans are watching) which it knew to be false. In some cases, it later claimed it never said they were true. Many times it allows its "contributors" to tell the lies without correction. Other times Fox says it was covering a "rumor" as important "news" (with the news "value" of many people believing the rumor, partly due to Fox stirring up the rumor), later asserting that it never claimed the rumor's veracity. (Sure keeps it in the public awareness, though.)
As far as knowing the difference between straight news and opinion shows, I'd say many Americans do not distinguish between the two (although they might "know" the difference), especially if the opinion shows--Fox's entire evening format--conforms to viewers' ideology and preconceived biases. Also, the bottom-of-the-screen news runner sometimes does the trick of editorializing.
In sum, Fox's overall modus operandi is not journalism--requiring verification--but at best editorialization and at worst propagandizing. Fox is what it is--a political campaign. That's okay, but journalism it is not.