I was at one of my usual stopping places online, Arts & Letters Daily, when I noticed a headline mentioning Stephen Greenblatt, the Harvard professor who wrote Will in the World, a strange and wonderful biography of Shakespeare from a few years back. I'm a Greenblatt fan, so I clicked.

The link took me to The New York Review of Books and a Greenblatt essay called "Shakespeare and the Uses of Power," which opens with a high-grade anecdote about Bill Clinton and Macbeth. I was cruising along nicely when, about 10 paragraphs in, I felt an urge I always get with longer pieces on the Web—a desperate craving for paper. I hunted around for the hard copy of the review but discovered that we'd let our subscription lapse, so I went back to the screen and printed the piece out.

A few days later, Greenblatt was on Open Source, the nationally syndicated public-radio show hosted by Christopher Lydon, to talk about the essay, and I tuned in. I've been on that show myself more than once, so maybe I'm biased, but I think Lydon is a marvel. I e-mailed him the next day to say that I'd loved the conversation, and he wrote back that there was follow-up stuff on the show's blog. I went there and read it.

Now think about the way this little media journey unfolded: from a Web-only media site, to the online version of an old paper periodical, to paper itself, to radio, and then back to the Web.

The standard view of the media today is of two separate, warring kingdoms. Bloggers and their ilk want to take down the uppity mainstream media, the "MSM" that they despise—traditional newspapers, magazines, and such. And the MSM curse the day that the digital barbarians stormed the castle and spoiled everything.

It's a great story line. And if you reflect on it for about one second, you realize that it's not true. Old and new media have a symbiotic relationship. Without The New York Times, The Washington Post, CBS News, and the other media ancients, bloggers who cover news and politics would have nothing to talk about. Meanwhile, the mainstreamers have their own Web sites, and they adore the traffic they get from bloggers linking to them.

I've written about this dynamic before, as have others. But there's one aspect of the symbiosis that is rarely mentioned: the way it helps us consumers by serving as a two-way filter. New and old media vet one another's work, each helping us to unclutter and winnow the content from the other side. When a major print outlet shines its light on a particular Web site or podcaster, I sit up and notice. Why? Because there are millions of bloggers and podcasters out there, so the establishment media can afford to be very choosy. A blog has to clear a high bar to win that kind of attention.

Thus, when I noticed that The Wall Street Journal (hard copy) was praising an architecture blog I'd never seen called BLDGBLOG, I opened my screen and typed it right in—it was a winner. After seeing a BusinessWeek (again, the paper version) story about a podcaster known as Grammar Girl, I told my 9-year-old about her and now we listen to her together.

Likewise, the online media don't link to just anything in the mainstream. Because many digital types are constitutionally suspicious of that world, when they praise something that appeared in print, it's noteworthy. And when they mock old-media content or call it an outrage, well, that's interesting, too. As I wrote this column, the news tab at Technorati.com was reporting that tons of bloggers were linking to a Time magazine story titled "An Administration's Epic Collapse." I don't know why—I haven't even glanced at Time this week. Now I will.

The filters aren't foolproof, but sometimes they work in spite of themselves. The Wall Street Journal recently ran a front-page teaser for an article about "relevant" Web sites for 2008 campaign coverage. I flipped directly to the piece and thought it was a big yawn. The Web fare that it touted sounded so dull that I didn't even go online to check it out. Happiness is knowing what to ignore.