Hollywood’s habit of spoiling movies by giving away essential plot points ahead of release is nothing new. A classic example is the trailer for Robert Zemeckis’s Cast Away, which reveals that Tom Hanks’ shipwrecked FedEx exec eventually escapes from the island. The Terminator franchise has been one of the worst offenders here: newer fans will recall the farrago over the producers’ decision to give away Terminator: Genisys’ big twist, that Jason Clarke’s resistance hero John Connor has been compromised by the machines. But the sci-fi saga has been at it for decades: one trailer for Terminator Salvation revealed virtually the entire story arc of Sam Worthington’s Marcus Wright, while James Cameron himself couldn’t resist giving away the fact that Arnold Schwarzenegger’s T-800 had swapped sides in 1991’s Terminator 2: Judgment Day.

The difference over the past few years, however, is that the use of spoilers in pre-publicity has become more flagrant and less subtle. In some cases, giving away the plot appears to be a deliberate marketing tool to encourage audiences to hand over their hard-earned cash. The days when every trailer was essentially a teaser appear to be long gone.

A classic example is the new trailer for Spider-Man: Homecoming, which reveals an epic tapestry of plot points that could surely have been kept under wraps without damaging our sense of anticipation. This is, after all, Spidey in the Marvel Comics Universe, a new wall-crawler who has already spun his magic in that gloriously zippy Captain America: Civil War cameo. People are already excited by the film. Do we really need to know that he messes up and loses the brand-new Spider suit donated by Robert Downey Jr’s Tony Stark as a result? And that our hero decides to go it alone against Michael Keaton’s malevolent Vulture anyway? The answer, clearly, is no, we do not.

One can understand the marketing team’s trigger-happy approach. Spider-Man getting a scolding from Iron Man – and potentially losing his Avengers membership card before he’s even had the chance to take advantage of the discounts available down at the local shawarma emporium – is something we’ve never seen in the Sony movies. It makes this latest reboot seem necessary, establishing its credentials as more than just another big-screen retread. But there were surely better ways to flag up Spidey’s callow nature and the challenges he’s likely to face.

Similarly unnecessary was Ridley Scott’s orgy of exposition at CinemaCon last weekend, where the veteran director was presenting footage from the upcoming Alien: Covenant. Scott appears to have revealed that Michael Fassbender’s David the android is the true creator of the xenomorphs, or at very least he played a powerful part in their inception. A prologue scene for the new movie reportedly shows David spraying gaggles of Engineers with black goo after arriving on the godlike aliens’ home-world in the ship he and Noomi Rapace’s Elizabeth Shaw borrowed back on LV-223. This, of course, opens up an entirely new set of questions – are we now expected to see the Engineers as victims? Did they somehow foresee their own destruction at David’s hands, explaining their cruel behaviour towards humanity in Prometheus? – but it still seems like a bizarre move to give away one of Covenant’s big twists before anyone has even seen the movie.

It’s more than possible that Scott’s approach to spoilers was informed by the reaction to Prometheus. Damon Lindelof’s screenplay took great pleasure in setting up intriguing – if mostly completely ludicrous – scenarios, then steadfastly refusing to resolve them, leaving most of us, if not outraged, certainly pretty bemused. Perhaps Scott simply wants to prove to potential audiences that this time the emperor will be wearing clothes, and that the new movie is therefore worth going to see. Never mind that most of us would rather have received answers to our many questions about Covenant the old-fashioned way … you know, in the course of viewing the actual film.

As a tool to build box-office hype, such an approach appears far from bulletproof. Batman v Superman: Dawn of Justice did reasonably well at the box office despite giving away most of its story arc in the title, then filling out many of the remaining gaps in a much-criticised trailer. But even with Cameron himself hyping up the virtues of its big reveal, Genisys did not appear to receive any real bounce – possibly because many members of its potential audiences wondered if they were really safe handing over two hours of their lives to the kind of producers who would make such a huge pre-publicity blunder. Cameron may have been right – the Connor twist did bring something new to the table. But you wonder if critics might have been kinder if the film’s major event – the turning of the saga’s answer to Luke Skywalker or Rick Deckard – had not been spoiled for them in advance.

Watch James Cameron discuss Terminator Genisys.

Perhaps Hollywood needs a new class of trailer – let’s call it the “troller” – which can be free and easy about its spoiling tactics. Then those who want to know everything that happens in a given movie before entering the multiplex can fill their boots, and those who would prefer to enter the auditorium relatively fresh can stay away.

Except of course, that no one in their right mind would ever watch this new, more honest form of promotional material, because fans only watch trailers in the first place under the expectation that the movie being promoted will not be spoiled for them. On current evidence, it appears that assumption is an increasingly risky one, to say the least.