It's called shoddy reporting. Unfortunately, it is offered up as regular fare by reporters these days both print and broadcast. The men that taught me this trade wouldn't hear of using an anonymous source, but they are dinosaurs left over from an earlier age. For them, it was the mark of a lazy or incompetent reporter. A good reporter can find a good source, they said a good source willing to be quoted.
News outlets have one commodity to sell and that is their credibility.
Without credibility, it's over. Unfortunately, the media, print and broadcast, has been chiseling away at its own credibility for the last 30 years in this manner. Ever since Watergate the anonymous source has been journalistic chic. The Watergate story couldn't have been broken when it was if the reporters had waited around digging for a legitimate source. But it would have been broken.