Blogs tend to take a bad wrap from the main stream media. However they do keep the press honest. Take this example recently from the NY Times, where a journalist mis-represented the testimony of FISA judges before the Senate Judiciary Committee regarding Bush's wire tapping.
Powerline had read the transcripts of the testimony, and scrutinized the article in two posts. A publisher of a small newspaper read those posts, called the Times senior editor and pointed out what the transcript actually said.
The Times editor called back and said that he was right, and the correction appeared in a later edition. It's unfortunate that not many people will actually read the correction, and therefore will still have the wrong impression about the authority that Bush has to initiate wire tapping, but at least there is some recognition that a wrong happened. Wonder if the article's writer is going to get talked to or reprimanded in any way.