The New York Times published an article last weekend that makes an interesting companion to the previously mentioned LA Times article about word-of-mouth. (They were even published the same day.)
In the article, Elvis Mitchell, film critic for the Times, discusses how the success of DVDs is changing movies. He makes a lot of claims without really backing them up and ends with an ominous note about DVDs eclipsing movies themselves. (This time, TV is really going to kill the movies.)
Both this article and the LA Times piece argue that audiences are getting smarter. Mitchell focuses on the popular "commentary track" feature of many DVDs, which is making film knowledge available to a much wider audience. This I like. A more knowledgeable film audience should result in better movies. (I hope that DVDs have a more substantial impact than text-messaging does.)
But the real effects of the commentary track will be slow and subtle — let's look back in 20 years. Mitchell is less convincing when he claims that DVDs are already changing movies.
For example, he claims that 28 Days Later is the "first case" of a movie in a theater containing a DVD-like extra. (Several weeks into the movie's run, the filmmakers added an alternate ending that runs after the closing credits.) But is this really any different from other attempts to get people to see a movie a second time? The Pixar folks often add a set of faux bloopers to the closing credits after the movie's first few weeks. Clue offered different endings in different theaters in 1985. Even movies like The Sixth Sense, Vanilla Sky, and Swimming Pool have world-changing plot twists near the end that allow their marketers to encourage people to see the movie a second time — you'll see an entirely different movie, knowing what you know now.
These gimmicks aren't caused by the popularity of the DVD. They're just attempts to goose waning box office receipts after a movie has lost its New Movie Smell(tm).
But I do think DVDs could make a profound impact on movies, eventually.