Lots to respond to in your two recent messages.
Most of the time I think the only obligation of a work of art is to tell the truth, but sometimes I think it also has an obligation not to include people lip-synching to Motown songs. I took my son to see Mask of Zorro last night and there was a coming attraction for Stepmom with Susan Sarandon and Julia Roberts that had such a scene. I'm sure I'll enjoy the movie--my tolerance for mushy family dramas exceeds yours for the gory and macabre (the Slate film critic is from Mars, the Movie Mom is from Venus). But I think it's time to come up with another way to depict family intimacy, wit, and hipness.
Truth is a tough one, though, and I guess that's why we have art in the first place. Look at your own example of the book by David Helfgott's sister. Who knows what the truth is for the Helfgott family, except that each person probably has his or her own view on it. I am willing to accept that and still allow the movie to be "true" to the artistic vision of the screenwriter, director, and actors. Same with A Man for All Seasons or Young Mr. Lincoln (guess what, More and Lincoln were more complicated than that). Like you, I was interested that several of last week's obituaries for Robert Young mentioned that he struggled with depression and alcoholism, and that his real life was a long way from the ever-wise and ever-patient father and doctor he portrayed on television. (I was also annoyed that they completely neglected his earlier career as a superb light romantic actor in movies of the 1940s.) Add Robert Young to the list with Bing Crosby, Dean Martin, Pee Wee Herman, Hugh Grant, and every other performer who pretended to be something we all wanted to watch just so that we would watch them. They don't make up their lines, either--that's why they call it acting. I have no problem with that. There are still plenty of depictions of depression, alcoholism, and every kind of dysfunctionality (I also have a greater tolerance than you do for those movies where people reveal family secrets and yell at each other and then cry and learn great lessons) to remind us that the idealized, Father Knows Best, Norman Rockwell world of tolerance and understanding is glimpsed in real life only in moments. I am still struggling to determine how "true" art has to be or can be, though. JFK still bugs me a lot. Even Frederick Wiseman documentaries are only "true" in a subjective sense. The selection of shots, the tempo, the juxtapositions all impose his vision of what he has seen on the reality going on around him. Is Casablanca less true than Apollo 13 or Invasion of the Body Snatchers?
As for "feeding the alligators of the mind," I agree with Bruno Bettelheim (the sole and only time I agree with him) about "the uses of enchantment" and the importance of allowing children to use fairy tales and Grand Guignol to work through emotional stages and understand societal norms. In a funny way, adults take these stories more literally than children do. Just look at Roald Dahl books like Matilda and The Witches. Parents shudder at the barbarity, but kids love them. It's adults who always ask me why the children in movies are missing one or both parents--kids usually understand that parents have to be gone so that the child in the movie can have the adventure without anyone there to tell him not to do it because he might get dirty or hurt. The Farrelly brothers feed another kind of alligator, and while I'll bet I will enjoy the movie less than I enjoyed your review (especially your apostrophe to Cameron Diaz), I agree with you rather than David Denby on what it's about and how the audience responds.
Somehow, both of these topics seem depressingly relevant to today's stories about Clinton, Starr, and Lewinsky. More on that later.
P.S. As someone who follows this stuff for a living, I can tell you that your analysis of conglomerates and break ups is quite literally right on the money.