I read Piers Morgan's first book (don't judge me!) and he touched upon this subject when talking about his newpaper days.
Paula Yates used to call Piers and tell him where she'd be and her "story" and that's how his papparazzi got pictures of her in the most random places (geographically, not biologically) and the "close source" in the article was Paula herself.
Paula was not the only one to do this, but it's the only one I can him recall mentioning by name.
Ever since I read that chapter, whenever I see an article where a "source" has given information, I always wonder if it's the celebrity themselves.