This reminds me of when I was in college - I majored in Journalism (back when they taught journalism). One of the examples used by a professor was about using unnamed sources. It seems that a couple of reporters (Washington newsroom) got a very good story that they "knew" was true, but they only had one source and their editor would not run a story with only one, unnamed source (the days of real journalism standards). To resolve this dilemma, one of the reporters interviewed the other about the story and they then quoted a "source close to the White House" (the office they were in was just a few blocks from the White House). The story got published.
That is what I think of unnamed sources.
With the popularity of 24hr cable news interviews that tact has been taken to a new level. Now, sleazeballs like Chuck Todd who want to create their own scandals or gotchas while doing an interview can use a preface like; “How do you respond to people who are saying...”, or “It has been reported that...” and then they put in their own self serving accusation without it ever having been raised before. Or even worse it could be something they got off a web source like “Occupy Democrat” or “HuffPo”.