Over the years anonymous sources have provided some of the most important information in The Times. The linked article by Public Editor, Clark Hoyt, offers an interesting insight into how the times manages their sources. From the article:
The policy requires that at least one editor know the identity of every source. Anonymous sources cannot be used when on-the-record sources are readily available. They must have direct knowledge of the information they are imparting; they cannot use the cloak of anonymity for personal or partisan attack; they cannot be used for trivial comment or to make an unremarkable comment seem more important than it is.