Jane Galt has the most tightly argued post debunking the fear that blogs will replace the media that I've yet seen. It's one of those must-read thingies the kids are always talking about. I'd add that the warlike relationship so often assumed between blogs and the media strikes me as a backwards interpretation -- the two genuinely need each other, and act more as countervailing powers than anything. Before blogs, the problem with the media-as-watchdog was that it lacked a watchdog -- a few self-interested organizations arose to work the refs, wielding outsized influence because so few replicated their strategies, but there weren't a broad range of informed observers attentively watching the press and lambasting its failures. Now, of course, there are.
And that's a good thing, for the press particularly. It'll force it to be more rigorous, less stenographical. At the same time, the press keeps the blogs in check, continually developing a baseline set of facts bloggers' partisan narratives can be checked against and occasionally reporting or investigating misdeeds by prominent online pundits. That's how it should be, we need to be kept honest too.
Lastly, in a period of declining circulation, the popularity of online punditry may well be a boon, particularly for magazines who, through blogs, have found and familiarized massive new audiences with their formerly-declining products. For all the talk of TNR's shrinking circulation, the couple thousand subscriptions they've lost over the past five years are a blip compared with the hundreds of thousands of new readers Atrios and DailyKos have sensitized to their existence, offenses, and influence. The very fact that Markos has to declare them irrelevant proves that they're not. And while you'd expect the blogs and the opinionated magazines to be direct competitors, nothing is healthier for, say, TAP, than this massive horde of youngish, affluent devotees who populate the blog and now know the publication. Hell, the blog is how I found the magazine, and now I not only read it, I write it. And while that may be bad for the magazine's quality, it suggests a symbiotic, rather than oppositional, relationship with the blogosphere.