I read some of them, yes. Do I put credence in them? Some of them, yes. I use blogs to supplement what I get from the national news media, but I know some folks who get all of their news from blogs and never pick up a newspaper or log on to a news website.
I think blogs absolutely play a role in politics, and in other aspects of everyday life as well. And it's a role that will increasingly grow. Granted, 99% of the blogs out there are blogs that nobody reads. They're maintained by average joes with absolutely no insight but who want to share their opinions. Some of them maintain their blogs with integrity, many don't, but it doesn't really matter since very few are actually looking at them. These same folks were spreading their opinions before blogs; they just called them "personal websites" back in those days. Then blogs came along and sites and softwares like Blogspot and Blogger and WordPress made it easy for them.
Then you have a middle tier. These are the guys that are logging some fairly decent amounts of hits on their blog, but their audience is primarily other bloggers of the same genre. They just read each other's blogs, link back and forth to one another, and feel good about themselves because they think they're reaching a broader audience, when in reality it's just one big gratuitous circle.
And then there are the few that make up the upper tier. The cream of the crop. These are blogs like Glenn Reynolds (Instapundit), Little Green Footballs, quite a few of the Pajamas Media blogs. I would even put the Huffington Post in that list, although I think that the regular readers and commenters of the HP are about the most insidious group I've seen anywhere (the folks of HuntingNet.Com's politics forum perhaps withstanding

).
I don't think most people realize just how influential blogs have/are become(ing). Look at the number of political candidates that have staff maintain blogs. Mostly they're Democrats, because Democrats tend to be more in touch with stuff that's hip and blogs typically are seen as pretty hip. But the same applies to Republicans. Look at how many newspapers and cable networks are incorporating blogs into their websites. That's a sure-fire way to know how big a part blogs are playing, because these same folks (the mainstream news media) are the same ones who tried to ignore the problem for so long and said blogs would never take off. Suddenly, they're playing the old "if you can't beat 'em, join 'em" strategy. Most of us use the Drudge Report. Drudge's site isn't a blog in the way we see blogs today, but in his day in the late '90s, when there were no blogs, he started what would ultimately become a weblog. Drudge's site was the real beginning of non-mainstream news media. Does anyone think for a second that Drudge hasn't had a powerful influence on American politics?
Unfortunately, it didn't have to come to this. If the mainstream news media was doing its job properly, there would've never been a niche for bloggers to fill. But the mainstream news media, somewhere along the line, decided that partisanship was more important than "all the news that's fit to print" and that niche evolved. Think back to North Texan's post last week about the Lubbock newspaper's recount of the 1966 UofTexas sniper. The reporter's comments pointing out the obvious, that the "smoke" rising from the "sniper's rifle" in the photo wasn't smoke at all, didn't post his comments on a blog; he posted them on a messageboard like this one. But that incident is a perfect example of how the mainstream press is out of control. Inaccuracies like that are brought to attention every single day in blogs. And the only ones getting the full truth in a lot of those cases are the folks reading the blogs, because most of the inaccuracies, even the intentional ones, aren't nearly as obvious as the Lubbock incident last week.
Think back to last year, when Israel invaded Lebanon and Palestine and the AP's stringers in the region who were Arabic sympathetic to the terrorists' cause were sending in all these photos that were doctored or staged to make the plight of the Lebanese and the Palestinians look much worse than it actually was. Those photos were being distributed to news outlets all over the world, including the biggest news outlets in the U.S. If it weren't for bloggers exposing those inaccuracies, it would've never been stopped.
So I would submit that not only do bloggers fit a niche, they fit a NEED. And I hate to say that, because as bloggers grow in popularity, my industry declines. As new technology enables bloggers to get their content out, cost-free, via podcasts, to PDAs and other handhelds, to your laptop via RSS readers, etc., newspapers become even more endangered. If a blogger with knowledge and insight can take a televised event, such as a presidential debate, and provide in-depth analysis of that debate, and send that analysis straight to my Blackberry and my laptop, why do I need a newspaper? Nowhere has blogging been more crucial than in Iraq. There have been a lot of wonderful stories that have come out of Iraq, as far as what the soldiers are doing for the people there, those stories that make you feel good about what's happening there. Those stories aren't being told in the MSM; the're being blogged from folks who are in Iraq.
When NT posted the link to the Lubbock newspaper last week, in a sense, he was blogging. He was doing the same thing any blogger would have done. When I read the link, I emailed the editor and the reporter and asked them about the inaccuracy in the photo caption. I was not rude about it, but just pointed out that I felt it was an inaccuracy and asked if they would look into the real reason behind the "smoke." The reporter emailed me back and said only that they were simply rerunning the caption from the original photo in 1966. The editor didn't even bother to respond to me. The news media has gotten too big for their breeches. But if one of the mainstream, widely-read blogs like Powerline had gotten hold of that story, they would've made the newspaper sit up and take note.
I hear a lot of people say that blogs don't have any credibility. No, a lot of them don't. And they say, "how can we know which blogs to lend credibility to?" Except for personal experience built over time reading those blogs, we can't. But I'd ask, with the current state of American news media, with doctored photos appearing in America's biggest newspapers showing lines of caskets containing innocent civilians supposedly killed by Israelis, how does the mainstream media have any credibility? How do you know which news agencies to lend credibility to?
So, yes, blogs are crucial, if it's only to force the news media to try and regain credibility that's been lost. As for blogs like the one you specified, they have no more a haven to make libelous or slanderous claims than any "official" news outlet would have. File a lawsuit against them and you'll probably see them cease to exist real quick. Sorry to ramble; this is a subject I dwell on and research a lot.