Truth in Harry Potter

Yeah, I'm not done talking about the book yet. As an offshoot of yesterday's conversation, the subject of Rita Skeeter came up. She's another character, who while ostensibly not on Voldemort's side, per se, has at the very least a greyish tint to her character. One of the more interesting things is the question, "Does Rita Skeeter lie?" Think about it. She may not tell the whole truth, and she make take things out of context, but does she ever out and out lie? Typically, she takes an actual incident (out of context) and then poses questions. Harry ran from Dumbledore's death scene (fact). Could there have been more to it? Was he somehow involved? I was struck by the fact that she did often tell the truth (kind of).

Which leads to a bigger question of truth in the book. Many people lie, or at least avoid telling the whole truth. Look at Dumbledore. Look at Snape. Did lying make them automatically evil? Did it work for the "greater good" or did it impede the greater good? How is lying portrayed in the book? It is always necessary for everyone to know the truth, the whole truth, and nothing but the truth? What would have happened had Harry known that he would survive Voldemort killing him? It might have made his actions less noble, but would it have changed the outcome?