This post contains spoilers of the soon-to-be-released Michael Bay sci-fi extravaganza The Island and the not-so-soon-to-be-released Jodie Foster psychological thriller Flightplan. I haven't actually seen either of these movies, but I have seen their trailers, which seem to give away their movie's major plot twists.
Based on the trailer, The Island looks like a cross between contemporary sci-fi action spectaculars like The Matrix and old-fashioned 1970s "messagey" sci-fi movies like Soylent Green. Ewan McGregor and Scarlett Johansson are even dressed in jumpsuits that look like the ones from Logan's Run. Its premise is that the characters who seem to live in an overcrowded futuristic city, hope to win a state sponsored lottery where the reward is a chance to live in a utopian paradise called "The Island". The movie's twists--which are both revealed about halfway through the trailer--are that (1) "The Island" doesn't really exist (funny thing about those utopias) and (2) the main characters are actually clones of people living full, happy lives in the "Real World".
The trailer for Flightplan waits until it is about 2/3rds of the way through before it gives away the movie's big twist. This movie's premise is that Jodie Foster and her 6-year-old daughter are flying on the maiden voyage of a brand new, super-duper, double-decker passenger airplane (that Jodie's character designed, 'natch!). Jodie and the kid get in their seats and decide to take a nap. When Jodie wakes up, about halfway through the flight, her daughter is missing. Jodie asks around, and everyone else on the plane, including a creepy air marshal played by Peter Sarsgaard, tells her that, "No, sorry, your daughter was never actually on this plane, in fact, she died six days ago!" At this point, the trailer seems to promise one of those is-she-crazy or is-it-a-ghost or is-it-some-kind-of-evil-scheme movies that keep the audience guessing right to the end. Whoops, no need to guess. The trailer then reveals one of the movie's plot points--Jodie discovers physical evidence that the daughter was indeed on the plane--which proves conclusively the "evil scheme" hypothesis. (Incidentally, the "discovery of conclusive evidence of an evil scheme" moment is almost exactly the same as a similar scene in the underrated, overlooked David Mamet conspiracy thriller Spartan.)
Now, I know this isn't a brand new phenomenon, but I can't help wonder: what does it mean when a studio is willing to give away practically the entire story in the trailer? I kinda/sorta get it in the case of The Island: it's a big, fx-driven sci-fi flick, and so maybe the studio figures no one really cares about the plot all that much. This fits in with my theory about Philip K. Dick adaptations: studios like to take a clever little sci-fi idea and wrap a big, noisy action picture around it. They aren't really interested in the kernel of an idea at all, though: it's just kind of an excuse for all the violence and explosions. I suppose it makes for better interviews if the actors can tell the press that they wanted to make the movie because it tells an interesting story about what it will mean to be human in a future where cloning/memory implants/precognition is possible instead of telling them that they wanted to make the movie because noisy sci-fi fx pictures attract big audiences.
Even so, one of the things that made the original Matrix movie such a success was that no one really knew what it was about until they were actually watching it. It gave audiences a kick to experience all the twists and turns of the plot without knowing where the story was going. It was this feeling of excitement that people took out of the movie with them, and then they told their friends to see it quickly, before they learned enough about the movie to spoil the surprises.
What I really don't get, though, is why the people who made the Flightplan trailer decided to give it all away. Flightplan doesn't seem to be aimed at the male adolescent, fx-junky crowd, but rather at adults looking for a smart, creepy movie--after all, Jodie Foster isn't exactly all that big with the kids these days. Flightplan looks like a Hitchcock-Twilight Zone-Sixth Sense-style psychological/supernatural thriller, and one of the big conventions--if not the big convention--of this kind of movie is "There's a Big Exciting Twist That the Audience Doesn't Know About". Letting the audience in on this twist before they've even seen the movie seems like poor form.
It's kind of a bummer, because Flightplan looked pretty interesting, but knowing, in advance, one of the major plot twists in a thriller really undermines the suspense. And what's the point of going to see a thriller that's had the suspense drained away by an over-explicit trailer?