The opening weekend! Nothing brings a Hollywood executive to the brink of an anxiety attack more effectively than this phrase. It’s the all-important buzz to which the movie industry has become addicted. And the studio bosses behind Spider-Man 3, released globally last week, must feel as if they have just hoovered up a giant hit of the most powerful cocaine known to man. Spider-Man 3 has reportedly made a gobsmacking $373m in ticket sales worldwide in its first weekend, kicking the ass of that other masterpiece, Star Wars: Episode III - Revenge of the Sith, which only made a paltry $254m. Never mind that most pundits thought that the film was dull - even Variety thinks the whole SM franchise is now "running on fumes" - its opening weekend figures have been hogwhimperingly fabulous, and that is all that matters.

The opening weekend is Hollywood’s neurosis. If a film has performed well on those first Friday and Saturday nights, if the all-important youth demographic of 18- to 25-year-olds has been piling into the multiplexes, those bosses will show up at work wreathed in smiles. But if the opening weekend figures have been poor, then Monday morning will find them hunched in the executive lavatories, crucified with irritable bowel syndrome. Bad opening figures will cause studio heads to make the universally understood "cut-throat" gesture, swiping the fingertips across the Adam’s apple. Forget it. Pull the plug. Yank it from the cinemas now. Get something else in there - fast.

Thirty years ago films were released gently, opening in cities and then rolling out across the country, here and in the US. It wasn’t uncommon for films to begin a second, stately progress across cinemas long after their first release. In the 1970s, you could see Mary Poppins or The Poseidon Adventure in the cinema years after they first came out. Before video, cinema managers in the US could schedule offbeat films at the cult "midnight" slot and wait for their popularity to grow. This was how Night of the Living Dead and The Rocky Horror Picture Show made their names.

Then two things happened: video and Jaws. Video rental meant that you didn’t have to go to the cinema to see a film. And Steven Spielberg’s Jaws pioneered the technique of opening a film on thousands of screens nationwide, to blitz the media with reports of hysteria about the film, excitement then fed back into the marketing campaign. Three decades on, DVD releases come only a few months after the film’s theatrical release. The window of opportunity is small. So every scintilla of energy has to go into that big, opening push.

And if the kids who see the film realise it isn’t much good? Well, that’s no tragedy. The tickets are sold. The next weekend’s figures may well drop off steeply, but the next product will come off the production line in a few moments anyway, and that production line is moving faster and faster.

Is it all bad for cinema? There are plenty of very decent films which get shouldered aside because their opening weekend figures have been poor. Joss Whedon’s sci-fi adventure Serenity, for example, was met with indifference because its first weekend numbers were unexciting. Only fierce support from fans kept it alive.

Good films will always find their audience - precisely because of the ubiquity of those same DVDs which drive the opening-weekend neurosis. What it means is that the long-suffering filmgoer will get blitzed with marketing hype for the latest picture - which is then utterly forgotten the following week. And these over-hyped prize marrows will crowd out other movie options in regional cinemas. The DVD choice will be rich, but the big-screen menu might be very dull indeed.