With the new Terrence Malick film, The Tree of Life, it's been reported that stars Sean Penn and Brad Pitt want you to know nothing about the movie going in, and supposedly it's not an easy one to explain regardless.
In the age of the Internet, it's very difficult to keep anything a secret, and people that love movies are often dying to know whatever we can about an upcoming flick we're excited about. But keeping yourself in the dark about a movie can be great fun as well.
I've gone into several films knowing nothing about them, and I was very pleasantly surprised in those situations.
When I was younger, my father would open the paper, and if a movie had good reviews all over the ads, we'd go check it out.
We went into Fatal Attraction like this, and from the ads I figured it would be some Wuthering Heights kind of romance, and deep into the movie we realized we were in for much more than we bargained for. (We also saw GoodFellas opening weekend because of the reviews in the paper, and I've been a lifelong Scorsese devotee ever since.)
I also knew nothing about A History of Violence other than it was a graphic novel, and it was great to see it without knowing anything about the story, which kept me on edge for much of the film. Was Viggo Mortensen really an assassin, or was it a case of mistaken identity? Did he have a twin brother who was a killer? It was really fun waiting for the outcome.
When The Sixth Sense came out, there was no all points bulletin telling audiences not to tell the secret at the end, but the movie had enough audience goodwill that no one was going to spoil it. A friend of mine even said he wished he knew nothing about the film before he saw it, because even though he didn't guess the end, he would have enjoyed the film even more going in with a blank slate.
With The Crying Game, the whole ad campaign was based around "Don't Tell the Secret," and the most recent example I can think of was the last Harry Potter book, where no one dared spoil it, and audiences would have gone to any length not to know in advance.
Christopher McQuarrie, screenwriter of The Usual Suspects, probably said it best about how movies shouldn't answer all your questions, and should leave things up to your imagination: Without mystery, there is no love affair.