Below are the first paragraphs of Janet Malcolm's lacerating assessment of the relationship between journalist and subject, The Journalist and the Murderer (1990). It was controversial when it appeared, but I think most nonfiction writers knew instinctively that Malcolm was right. Journalists depend entirely on their subjects for the essence of their work, and they expect to get it unconditionally. Whatever social or artistic value the writer creates is independent of that exchange: it can't alter the exploitative contract to which the subject is generally an unwitting party. The best you can do as a journalist is acknowledge the damage you may be doing and limit it when possible. That's a pretty anemic, ignoble remedy, but it's a lot better than claiming moral exemptions you don't have.
Every journalist who is not too stupid or too full of himself to notice what is going on knows that what he does is morally indefensible. He is a kind of confidence man, preying on people's vanity, ignorance, or loneliness, gaining their trust and betraying them without remorse. Like the credulous young widow who wakes up one day to find the charming young man and all her savings gone, so the consenting subject of a piece of nonfiction writing learns—when the article or book appears—his hard lesson. Journalists justify their treachery in various ways according to their temperaments. The more pompous talk about freedom of speech and "the public's right to know"; the least talented talk about Art; the seemliest murmur about earning a living.
The catastrophe suffered by the subject is no simple matter of an unflattering likeness or a misrepresentation of his views; what pains him, what rankles and sometimes drives him to extremes of vengefulness, is the deception that has been practiced on him. On reading the article or book in question, he has to face the fact that the journalist—who seemed so friendly and sympathetic, so keen to understand him fully, so remarkably attuned to his vision of things—never had the slightest intention of collaborating with him but always intended to write a story of his own.