Since The Pirate's Gold set sail a century ago, maritime piracy has been the subject of several hundred films. Celebrating this activity assiduously has enabled Hollywood to make off with much booty. The first three Pirates of the Caribbean titles alone grossed $2.6bn at the box office, while their Blu-ray versions and merchandise are still bringing in the doubloons. Yet the eager purveyors of big-screen buccaneering don't seem to like it in real life.

The industry's captains are appalled by piracy that's actually aimed at themselves – so much so that they now treat their own customers as potential thieves. If you want to see a film these days, expect to be threatened first. Point your iPhone at the screen, and you'll find yourself walking the plank. Perhaps you'll get your bag searched lest a covert camcorder lurks therein; maybe you'll be spied on with night-vision binoculars to check that you're snogging and not snapping in the back row. If you try to avoid such hazards by sticking to DVDs, you'll be driven mad by unskippable, preliminary admonitions.

Naturally, film's bigwigs see no resemblance between their own bounty and that plundered by pirates ancient or modern. After all, their business is legal and therefore their cause must be righteous. So the rest of us are expected not only to comply with their irksome prohibitions but even to grass up any "knock-off Nigel" we may happen to encounter. However, the ethics of piracy are less straightforward than the big-screen boss class would have us believe.

The victims of the real-life Caribbean pirates also had the law on their side, but their moral case was far from watertight. Often, the treasure of which they were stripped had been extracted from mines worked by slaves in stolen colonies. Their dispossessors could be considered to be redistributing ill-gotten wealth from the undeserving rich – usually to themselves, but sometimes to the poor as well. Arguably, the pirated were at least as piratical as the pirates. Our whingeing movie moguls are also morally compromised.

Fancy seeing Pirates of the Caribbean: On Stranger Tides? It's on at the Empire Leicester Square in London, where a couple of seats in the circle for you and your beloved will set you back £35.30. If you're going to bring the kids and throw in popcorn and Coke, you'd better take out a mortgage first. In your own hometown you might pay less, but over the last 30 years box-office prices have risen by almost twice the general rate of inflation. Meanwhile 3D, resuscitated partly to beat the copyright pirates, has been turned into yet another means of cranking up revenue.

The unfortunates who sell you the popcorn won't keep much of what you hand over. Others will be more blessed. Disney's CEO, Bob Iger, picked up $28m last year in pay, bonuses and shares. Johnny Depp did rather better, pocketing an estimated $75m. Pirates 4 alone is apparently netting him $35m. Jack Sparrow eat your heart out.

And Depp isn't even close to Hollywood's biggest earner. Last year, James Cameron is thought to have collected over $250m, almost all of it from a single film. He and his ilk are doubtless deserving, but surely they can't be quite as deserving as that. So why do they grab all these pieces of eight from the world's hapless film fans? Answer: because they can, just like the pirates of old.

Such is the industry that's now falling prey to the copyright buccaneers. That the latter are making headway cannot be denied. Today, new releases can be viewed via five mouse clicks from anywhere in the world. Film piracy is said to be costing the US economy over $20bn a year. Apparently 3D isn't actually going to save the day, and a forthcoming attempt by the studios to pre-empt online pirates by pirating the rest of the industry may create more problems than it will solve.

Clearly, copyright piracy is going to change the film biz, but it's not so obvious that all the changes will be for the worse.

As the music industry has found, prices may have to be reduced to make illicit material less of a compelling temptation. This may mean that some of the people who have abandoned film-going will make their way back to the 'plexes. It may also mean there'll be less money for star-studded, sprawling extravaganzas such as Pirates 4 (budget: $200m-plus). Perhaps in their place we'll get films forced by financial constraints to rely on real characters and proper stories. Anyway, the lowering of barriers to entry should open the way for fresh talent and new ideas.

Oh, and there's one more likely consequence. Hollywood's grasping gentlemen o' fortune will receive the black spot. Shiver me timbers and yo ho ho!