Let's talk about hypothetical risks. If you go to a big preview screening in Leicester Square – a privilege given to the press, entertainment industry VIPs, and a fair number of punters who win radio phone-in prizes – you'll be asked to leave your mobile phone in a baggie behind a counter at the front of the cinema.

The film industry says that this is a necessary precaution against the hypothetical losses that would result should someone use a mobile phone to "camcord" (that is, record from the audience) a pre-release movie and leak it onto the internet. The film Wolverine (panned by 63% of critics according to Rotten Tomatoes, which also reports a $177,288,905 box office gross to date) is often cited as an example of how a film can be harmed by pre-release leaks. Also cited is Motion Picture Association of America (MPAA) research claiming the vast majority of pirate movies on the internet and sold on the street start as camcordered movies (more on this later).

When pressed, spokespeople from the Federation Against Copyright Theft (FACT) and the Film Distributors' Association (FDA) admitted they had never heard of a pirated movie "in the wild" that originated with a mobile phone, nor, to the best of their knowledge, had anyone ever been ejected from a cinema for attempting this.

What's more, although FACT and the FDA stressed their belief that the majority of pirate movies originate with camcorders, they also admitted that this was never the case with pre-release movies: film previews have never been a source of film piracy.

The whole business of camcordering seems to be a red herring, frankly.

The supposedly damning pre-release leak of Wolverine? An inside job. Of the 26 Oscar-nominated films for 2009, 23 were available as pirated copies online on the eve of voting, 100% of them derived from "screeners" (discs given to jurors, critics, exhibitors, sales agents, etc). On average, screener copies leaked onto the internet six days after they were sent out to the Academy for review prior to awards voting.

Music piracy is characterised as "grave" by the industry (in the US, NBC went so far as to tell the Federal Communications Commission that film piracy threatened the livelihoods of heavily subsidised corn farmers due to potential losses in popcorn sales, and that this would have knock-on effects in the market for heavy farm machinery). But the studios have just enjoyed yet another record-smashing box office quarter, in the teeth of a global econo-polcalypse that has every other sector of the economy on life support.

But there is one indisputable fact: mobile phones are rapidly expanding their capabilities. Megapixel phones are the norm now, as are fast network connections and memory slots that can accept up to 64GB of storage. If a tenfold increase in battery life were to take place tomorrow, it would, indeed, be practical to record a feature film with a mobile.

Which brings us to the other theoretical risk: the risk of leaving hundreds of increasingly powerful phones in the safekeeping of a cinema, out of your sight for two or three hours while you watch gigantic robots throwing buildings at each other.

This risk is also substantial. From sim cloning (copying the phone's sim so that other phones can use your account, listen to your voicemail, and make calls that are billed to you) to data theft, the risks are enormous. Think of the data storage on your phone – that potential 64GB on a postage-stamp-sized SD card. That's enough to carry around libraries' worth of confidential or proprietary information – several times the amount of data lost in the enormous HMRC leak of family financial information last year. Add to that the contact information – personal phone numbers for all the people in the lives of everyone at the movie, including, for example, ministers of state and other VIPs who are routinely invited to previews. Then consider confidential diaries, family photos, personal voice memos, access to your search history …

Once you start enumerating the potentially sensitive information on a mobile phone, it's hard to stop.

Ironically, mobile phones have terrible security models. They don't support encryption for in-built or expanded memory, have short passwords that are often easily bypassable – a problem that's exacerbated by corporate IT departments who set bad passwords across the system (one enterprise I know of gives all its executives a BlackBerry with the password "QWERTY").

What's more, the more confidential – and useful – things there are on your phone, the less likely you are to want to leave it at home during a night out. Indeed, the very capabilities that make a phone useful also make it indispensable. It doesn't take a techno-visionary to see the train wreck in the offing.

As the movie industry reminds us, phones are getting more powerful all the time. Entrepreneurs look forward to phones that work as authentication tokens for signing into corporate networks (phones are already used to complete many security procedures today, as when Pins are texted to your phone), stored value cards that work like Oyster cards, allowing you to spend money just by waving your phone at a touchplate, and as trusted network conduits into the innermost layer of secured and sensitive systems.

Any phone that can do all this can also handily copy a film. Any phone that can do all this is a device that you'll never leave the house without.

Of course, there are ways of containing liability. If I wanted to stop movies from being pirated, I'd focus my effort on the places where they leak. In the case of the Oscars, that's the insider awards voters who leak every movie they're sent within six days, not the film critics – who have never, ever leaked a movie by recording it at a preview.

Likewise, if I wanted to secure hundreds of mobile phones, my first resort would be to leave them where they are, in cinemagoers' pockets, which is surely the safest place for them to be. Failing that, I'd have a top-notch security system, with tamper-evident, shielded, opaque bags for storing phones, a system of multiple watchers who kept an eye on each other as well as the phones, and special background checks into anyone allowed anywhere in the vicinity of the handsets.

Oh, and I'd make sure I was carrying special insurance that specifically covered losses due to data breaches from phones in my care.

What does the film industry do to safeguard your phone when you see a preview? It's very hard to say. No one could really tell me what the details were. Most helpful was the FDA, which was also able to confirm that it had never had a known data breach from a phone taken into custody during a preview. It also assured me that only staff from the security companies were allowed to handle the phones in care.

But it wasn't able to confirm the qualifications of the security staff, nor whether there was any special insurance cover for data breaches from these phones. And the baggies that are used are "like the ones at the airport" – standard, transparent Ziploc bags through which phones can be seen and worked. These bags lack tamper-evident seals, so it's also possible to remove a phone and replace it without its owner being aware of it.

The FDA's spokesman also stated that he believed people who had a need to retain their phones – say, government ministers, solicitors or doctors whose phone contained confidential information, or parents who are on-call to their babysitters – might be able to retain their phones.

FACT was less helpful on this score, noting that "no one is forced to see a preview". Undoubtably true, but rather beside the point. If I do choose to see a preview, it's fair to ask what precautions are taken with my property while it's in custody at the cinema.

The FDA referred me to Music and Arts Security, a firm with a long history of providing security for film screenings. There I spoke briefly with Paul McTaggart, who started off by saying he was "not obliged to give any comment" (I assured him that I didn't think he was, but rather hoped he would answer my questions anyway), and then told me that he would only answer questions if directed by one of his firm's clients.

So I emailed Debbie Turner, head of publicity for Paramount UK, asking her to authorise Music and Arts Security to tell me how its internal oversight of mobile phones works, whether they are covered for data breaches, whether exceptions are made for people who have good reason to keep their phones on their person, and so on. Instead of answering any of these questions, Ms Turner emailed this to me: "Both Paramount Pictures and Music & Arts Security feel that security procedures implemented at screenings is a confidential matter, on which we are unable to comment further. However, M&A have supplied the following statement: '[the] Private Security Industries Act 2001 stipulates all security operatives have to undergo as part of their application a criminal records check. Which is carried out by the SIA (Security Industry Authority). For further information contact SIA or visit their website.' "

Note this doesn't confirm that "security operatives" are the sole personnel in contact with phones, nor does it indicate the oversight procedures, insurance, exceptions policy and so on.

Indeed, the most remarkable thing about this whole business is how incoherent the policy is. Both the FDA and FACT assured me that phone surrender won't become a feature of regular screenings; nor will bag checks. But of course, a number of UK cinemas sport signs stating: "Please be aware that we are conducting a compulsory bag check at this cinema."

What's more, in Canada, a recent anti-camcordering law passed after intense lobbying from the same motion picture studios (the very ones that created Britain's policy on previews and mobile phones) has made bag searching a routine part of moviegoing. It has become so invasive that a Montreal theatre chain was fined C$10,000 (£5,230) after it searched a teenage girl in front of her parents and turned up her birth control pills – not a good way for any parent to discover that her child is sexually active.

It's hard to see where this will stop. One correspondent in Melbourne, Australia, reported having her handheld Nintendo DS (an older model without a camera) taken away on the way in to a film. Some might argue that theatre security can't be expected to be competent enough to sort devices capable of recording a film from devices that aren't, but I'd argue that someone that incompetent is also not to be trusted with our electronics while we're in the movie, either.

If I were a wily camcorderer who really wanted to shoot a preview, I'd simply not surrender my phone on the way in, since (according to the DFA, though not confirmed by Music & Arts) the phone surrender is on the honour system, and so you could simply say, "I took your advice and left my phone at home", and head into the amphitheatre with your mobile (and a knapsack full of spare batteries, I guess). Or if you were really cunning, you could bring two phones – an old model and a new one – and surrender the dud on the way in.

Better yet, though, would be to enter the cinema with any one of the hundreds of modestly priced hidden cameras that don't look like a pocket camera or a phone. These are cheap as chips, can be bought in most high streets (or delivered overnight by Amazon), and can manage surprisingly high quality at the top end of the range.

Better still: wait six days for a studio insider to leak his screener all over the web.

Of course, the risk to your phone and your data is wholly hypothetical. But then again, so is the risk to the film. Movies are pirated, data is stolen. As far as anyone can tell, neither has ever happened at a film preview. Whose risk is more important to you: Paramount's, or your own? And if Paramount wants to shift the risk to you, shouldn't they shell out for high-security baggies, and publicly disclose the measures they take to protect your property?