Jason Van Steenwyk via Glenn Reynolds points out that quite a number of high-profile journalists seem to be recycling the same quote from each other rather than going to the source. As a medievalist, I'd point out that Jason has identified descent due to shared error, exactly the way that we trace manuscript histories.
I'm someone who was going to be a journalist, and who has some training in the area (M.A., Stanford, 1991), so I know that this is a huge failure on the part of reporters (at least as far as their training goes).
I'm also someone who had exactly the same thing happen to me in January 2003, so I'm not at all surprised that so many big-time journalists are violating good-practice rules. It seems very common.
Back in 2003, there was a story in the London Sunday Times about my work on J.R.R. Tolkien's Beowulf translations. There were a lot of inaccuracies and problems with the story, but at least the reporter actually interviewed me. But after that, the story just took off. There were so many articles that I couldn't track them all down, and they invariably cobbled together quotations from the Sunday Times interview and from a piece of mine that had been published on the web, "Wrong About Almost Everything: Editing J.R.R. Tolkien". Of all the stories that came out, in many languages and formats, I'd say less than 2% of the reporters actually contacted me. I certainly was never interviewed in all the German papers that quoted me, nor in the Australian. But only 30% of the time did the reporters refer specifically to the Sunday Times story, and they never stated that they were quoting my published work without attribution, rather than interviewing me directly.
It may be that the specific case Jason mentions has to do with ideology rather than simple bad practice. It was my experience in journalism school and right afterwards that people at least acted as if they took attribution, getting the interview yourself, etc., very seriously. But there were no ideological reasons for reporters to do what they did in my case, and yet the same sloppy, dishonest practices were followed.