John Edwards' "affair" rumor given credibility by mainstream media repetition

The National Enquirer reported this week that John Edwards has been having an affair with a former campaign worker. This lead to Edwards denial, which led to the denial being picked up and legitimized by the Los Angeles Times and later, by the AP. The most interesting piece of this story is the sourcing.

The LA Times story is actually on the blog but if news media thinks that different standards apply to blogs, they don't understand that the public doesn't think a "blog" on the LA Times as anything but the LA Times. IN any case it's written like a story and was the initative for the AP picking it up. In this they also quote the AP article so it's perhaps the bigger picture.

Now originally the NE says it has a friend of the woman Edwards allegedly had an affair with. She's anonymous. When the LA Times quotes her, or sums up her statements, they're to a certain degree, giving credibility or at least counting on the credibility of the National Enquirer which is, I thin we know, not a very credible paper.
Secondly, since no one pays attention to the NE why in the world did the Edwards campaign make a statement that would only tarnish them? Well, would it make more sense for them to directly make a statement like this, or to refuse to answer and arouse suspicion? IN the day and age of blogs there's certainly all sorts of rumors floating around, should journalists ask about each one? Should there be some sort of verification process, even before reporting what a supermarket tabloid insinuated?