Soon it will all be over. Next Tuesday, the nation will decide whether John James, the handsome but peevish Australian, or Sam Pepper, the goofy prankster, or jolly Josie, the farm girl turned MC, or indeed somebody quite unforeseen is the housemate who should win the prize money of £50,000 plus a brief sojourn in the national limelight. And with that, Big Brother 11 will be over – the last-ever series – and an era will have come to an end.

It's an era, however, in which the wider meaning of Big Brother – in the Orwellian sense – has embedded itself in our national life, in ways of which we have only gradually become aware. In the last decade, we have become the most surveyed, monitored, CCTVd, inspected, followed, targeted, filed and cross-referenced society in western Europe. We have endured the invasion of our privacy to a degree that would once have seemed possible only in science fiction. We have become the unwitting targets of governments, banks and the police, along with a host of unnamed commercial concerns who sell data about us to advertisers on the internet. We can hardly conduct a single financial transaction, or make a single gesture of communication online, without it entering a databank and adding to an already considerable "file" that defines our identities as consumers, frequent flyers, early adopters, porn-downloaders, credit risks or potential criminals. Meanwhile, we live blissfully unaware that a shadowy assessing authority is out there, telling the world a combination of truth and lies about who we are.

We might be forgiven for feeling paranoid about this. But paranoia is actively encouraged by governments or organisations that like to wield complete power over the lives of its citizens. It's like being brought up Catholic and told that God is watching everything you do, while your conscience constantly patrols what you're thinking for evidence of inappropriateness. It's like the chap in Prime Minister Lee Kuan Yew's Singapore who, when I asked him why it was that the train stations were so immaculately free from litter, graffiti and thugs, tapped his head sagely and said: "It's the policeman who lives in your head."

George Orwell invented the term "Big Brother" in 1947 when he was writing Nineteen Eighty-Four, his classic evocation of a socialist hell in which a government strives to own the minds of its people, as well as change its country's history as it suits them. According to the novelist and polymath Anthony Burgess, "Big Brother" began with a billboard advertisement that Orwell would have seen during the Second World War – an ad for Bennett's Educational correspondence courses. It featured a photograph of the kindly-looking proprietor offering prospective clients advice, under the phrase "Let me be your father." When Mr Bennett died, his son took over the business, employed a photograph of himself looking stern and imposing, and changed the shout line to "Let me be your big brother". Between this and the memory of the posters of Lord Kitchener from the First World War, pointing a minatory finger at the viewer and intoning the words, "Your Country Needs YOU", Orwell had his perfect image of benevolent dictatorship – of a doctrinaire government telling its subjects that it will run your life for your own good.

In Nineteen Eighty-Four, Big Brother is the notional ruler of Oceania, one of the world's three superpowers, which wages almost perpetual war on the other two, Eurasia and Eastasia – or so they tell the people, in an attempt to keep them in a state of cowed alarm. Big Brother is the party hero, leader, guardian and originator of the Revolution, and a father-figure to his people. In the novel, at the end of the daily Two-Minute Hate, when the proletariat screams abuse at the televised face of the international villain Goldstein, Big Brother's face appears and the crowds chant "B-B" in a slow, rapturous chorus. "Partly it was a sort of hymn to the wisdom and majesty of Big Brother," wrote Orwell, "but still more it was an act of self-hypnosis, a deliberate drowning of consciousness by means of rhythmic noise."

The TV show, which started life in the Netherlands in 1999, began life as a game of survival and popularity under the eyes of total-surveillance cameras. Would people crumple under the pressure of being watched 24 hours a day, while they slept, ate, chatted, argued, picked their noses, flirted, fornicated and washed themselves? Would being cooped up with a dozen strangers of different ages and walks of life, lead to exciting clashes of temperament? The prospect of winning a large cash prize was supposed to be a spur to good behaviour, as the housemates strove to avoid being evicted from the house by a combination of peer hatred and viewer dislike.

With the benefit of hindsight, we can see that, for a decade, we've engaged in a shameless combination of voyeurism, lab-rat inspection, prurience and moral condemnation, as we've watched a Bedlam of egomaniacs, exhibitionists, dunderheads, sex fiends, liars, fantasists, mentally unstable and existentially challenged victims chat and bitch and canoodle with each other, perform degrading tasks and lay their lives and their (sometimes toxic, sometimes pathetic) personalities bare for our enjoyment. How proud we must be of ourselves.

In the early days, the nation was gripped; viewers talked about the housemates as if they were friends, or acquaintances, or were established stars with fascinating lives.

There was "Nasty Nick" who passed secret messages to his fellow housemates until he was exposed by the first-ever winner, Craig (memorably described by an online commentator as "poncing about as if he's got his white van keys stuck up his arse") and Brian the gay Ulsterman and airline trolley dolly with a tongue that could clip a hedge, and Nadia the Madeiran transsexual who liked to wear six-inch heels in the shower ("Go Nads!" her supporters used to shout ambiguously outside the BB House), and Pete the Tourette's sufferer with the engaging facial tics and the uncontrollable swearing, and, among a crowded field of ditzy young women, the birdbrained Helen Adams who tended to vocalise any thought that entered her head, including the immortal: "I like blinking, I do!" There was a certain dental nurse from Bermondsey who pronounced East Anglia "East Angular" and shouted, during a striptease drinking game: "Me kebab's showing!" Fans will recall with sweaty palms the astonishingly rude series five, in which a 24-year-old Zimbabwean cardiac nurse called Makosi had sex in a foaming Jacuzzi with a Geordie dancer called Anthony and coolly asked Big Brother next day for a morning-after pill, and a half-Kuwaiti, half-Polish woman called Kinga pleasured herself in the garden with an empty rosé wine bottle, a coup de théâtre later voted Most Shocking Moment in the show's history.

The most genuinely shocking thing about Big Brother, however, is how casually we accepted its dubious strategies. Each year, we tacitly agreed to watch a dozen or so strangers being manipulated by an all-seeing authority, forced to dress up and make idiots of themselves, denied food and drink on a whim, then plied with drink in the hope that they'd behave without inhibitions, and forced to shower in their underwear and defecate without locks on the doors. Did we know that they had their luggage inspected, as though by HM Customs, and weren't allowed to bring watches (so they wouldn't know the time when waking in the pitch-dark bedroom) or pens or other writing materials, including eyebrow pencil? Did we know (or care) that when technicians came onto the set to make adjustments, the housemates were "locked down" in their bedrooms, with the curtains drawn but with a klaxon sounding in case anybody fell asleep? General Pinochet would have nodded approvingly at such firm arrangements. And as for the housemates' conversations – did we realise that the nightly "highlights" of the day's action were heavily edited, to show certain housemates in a good, and some in a bad, light? That actual "reality" was kept at arm's length in this reality TV show? If we witnessed a "live stream" of genuine, as-it-happens action from the BB kitchen or living-room, the Endemol producers carefully used the sounds of birds twittering to drown out any deviation from the kind of chat they wanted us to hear. Did no alarm sound in our heads, saying, They're stopping us hearing what these people are really talking about ...

Along with the censorship and manipulation, we might have felt uncomfortable about our Peeping Tom role, as contestants succumbed to lust and, in 2004, Michelle Bass and Stuart Wilson, after some prolonged negotiation, disappeared under a table to have sex, protected from view by a single sheet. The nation's bookmakers had already offered odds on who would participate in the first "Big Brother bonk".

Some viewers wondered about the breezy presentation of housemates with mental illness. We were encouraged to regard Pete Bennett, the Tourette's syndrome sufferer, as a boyish charmer with some odd affectations of behaviour, and Nikki Grahame – a disturbed anorexic with mental health issues and one suicide bid behind her – as an "feisty" and argumentative young woman who ranted hysterically (but so amusingly) when denied mineral water, rather than as someone on the edge of cracking up.

What started life as a game show about charm and interaction had become something else: the spectacle of handicapped or unhinged people disporting themselves for the amusement of bored and prurient viewers.

Occasionally, critical voices were raised by ex-participants. "I think reality TV programmes do a lot of damage," said Vanessa Feltz, who starred in the first Celebrity Big Brother. "Nothing prepares you for the scrutiny and incarceration and worrying what people might think of you and trying to survive all at once. Believe me it was extremely intense and a most unnerving thing." Kinga Karolczak, she of the rosé wine bottle, told the press that she had been forced by the programme makers to behave outrageously and was plied with drink and offered free cigarettes if she agreed to walk around the BB house topless.

Germaine Greer, who did most to alert the public about the reality of the show, wrote that "the whole point of Big Brother is that he is a bully", and itemised the levels of dirt and degradation to which the contestants, including herself, were subjected. She described the lavatory conditions and the "combination of cruelty and incompetence" that induced bladder and bowel malfunctions – not to mention the vomiting, the incubation of bacteria, the botulism, the shivering and night-sweats. "As reality television series multiply across the networks," she concluded, "they will become increasingly sadistic and prurient. The only way forward for ordeal by television is down, which in [Orwellian] Newspeak is of course up, towards maximum exploitation of vulnerable people."

Five years later, that hasn't happened. Instead of ramping up the exploitation, Big Brother is quietly dying away. A combination of dull housemates and viewer disaffection has affected viewing figures. "Is anyone still watching that thing?" is an often-heard question. But something else has happened to us in the last decade, something loosely connected to Big Brother and its queasy record of manipulation, histrionics and boredom. We have become inveterate watchers of each other.

Just as BB contestants once used the Diary Room to confide their inner feelings to a notional superior (and judge of their actions), millions now offer their daily, sometimes hourly, two-penn'orth of news and wisdom to the outside world via Facebook and Twitter. Once, we'd come home from work and watch BB housemates cooking dinner and worrying about how long they should cook the pasta. It wasn't great drama, but we watched it anyway. Now we tweet each other with similarly gripping news of what we're having for supper and how we're cooking it. No specialised area of human life, no tiny detail of behaviour, is now so trivial that we won't report it to each other with high seriousness, as if it were a dispatch from a war zone.

And in the intervening years, we've quietly become a nation of housemates, endlessly spied on by authorities and by businesses. Today, if you call 999 to report a crime, you'll have your details instantly logged on a secret database that mingles the names of criminals with those of victims and members of the public, and your name will be kept there for 15 years, practically begging to be involved in a disastrous mix-up. Today, if you open a pub, the police will try to install CCTV in it to keep tabs on the drinkers. If you, the landlord, complain that you don't like this intrusion upon your customers' privacy, you could lose your licence. Other kinds of surveillance don't involve the police, but are just as creepy. Try buying any goods online today, and you'll find yourself pursued around the Internet by advertisers who know your details and buying preferences remarkably well, because they've bought them from monitoring agencies.

The most alarming fall-out from Big Brother, however, is that it has ushered in a surveillance society, to which everyone contributes. Earlier this year, a comedian friend reported that, on his journey home from a day at the BBC in London, a total stranger on the train pulled out his iPhone and showed him that his every move, every meeting, every conversation, practically every comfort break, had been followed by Twitter users. They'd been keeping an eye out for my friend when his train arrived at Waterloo; on the Tube to Shepherd's Bush; in the BBC car park; in the BBC canteen. I wrote about it – and soon learned from other half-famous people with similar complaints. One had looked himself up on a Twitter site and found: "My movements over the last five days, and that of my wife and child as we went to and from Brighton for three days of work, were all intimately tracked, as was our weekend in London. Two different tweets from the same London café observed my three-year-old mistakenly taking another child's milk bottle from a pram ... "

Public recognition has brought with it a culture of surveillance that's close to stalking. Once, celebrities might have worried about journalists and paparazzi. Now, everyone's a reporter and broadcaster and they can say anything about anyone, without rules. That's the real legacy of Big Brother. The surveyed have become the surveyors. "Them" has become "Us." Ten years of watching human guinea pigs and lab-rats at close quarters, living out their three-month imprisonment in a prefabricated hell, has given us a taste for prying into each other's lives and dramatising the trivial details of our own, while making everything public on electronic screens. And while this is going on, we're blithely ignoring the steady erosion of our privacy by government, police and business.