After watching Blade Runner recently on late-night television, I wondered: whatever happened to all those scientists' predictions that humans would be having sex with robots by now – or at least in the very near future? After all, Ridley Scott's film is only set in 2019.

I still can't imagine having a hot replicant boyfriend any time soon – a battery-operated vibrator is about as high-tech as it gets for me. Others, however, are fast becoming accustomed to using technology to take things a step further: men already go online to purchase custom-made "real dolls", which are like silicon Stepford Wives minus the vocal cords, and cost several thousand pounds. Fans claim they are a viable alternative for the lonely and socially awkward. But can it really be healthy to seek out intimacy with an inanimate object?

At the same time that technology is causing some people to withdraw from the dating game – preferring online porn and virtual sex to the real thing – the sheer volume of specialised websites means that huge numbers of people are now connecting in ways that they never have before. Though most deviant sexual behaviours have been around for ages (the Romans were having orgies, after all) the Noughties have ushered in the normalisation of fetishes – and made it vastly more easy to find others with similar tastes. These days, BDSM (Bondage, Domination and Sado-Masochism) has gone from underground fringe clubs to housewives browsing spanking paddles online and in high-street sex shops.

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Sex parties, too, have shed their image of dumpy, middle-aged couples circling a bowl of car keys, and now upmarket swinging events such as Fever and Killing Kittens cater to young and more conventionally attractive couples by using their website to vet applicants. These days, more and more single women are taking the plunge.

Technology has also made casual hook-ups – and infidelity – simpler than ever: a well-placed digital photo and a reasonably witty online profile can bring dozens of responses within a few hours. And there are niche markets for everything (among the more obscure I've come across: love connections for the freakishly tall and even for devotees of the American writer Ayn Rand).

But what a friend of mine calls "the crack cocaine of online dating" does have its risks. Ultimately, it's much easier to hide one's true intentions behind the anonymity of a keyboard, and to lie. I've met men who happily crop out years of their life (and children!) as easily as the woman standing next to them in their profile picture.

Of course, not everyone online is a cheater. Some people are completely open about their alter egos, and use their "avatars" to have cybersex on sites such as Second Life. And many see it purely as a form of escapism, and have no intention of actually meeting in person.

The internet does, of course, provide people with fetishes with an easy way of finding each other. I personally would not want to change an adult baby's nappy, but it seems there are people out there who want to breast-feed and role-play a nanny scenario. And it's much easier to send an e-mail through a website than to mention the subject casually on a first date.

In a world bombarded by hyper-sexualised images, even those who identify themselves as asexual or celibate are able to surf over the sea of pornography and connect with people who understand them.

Modern sex, to me, is about easy connectivity, and open-mindedness – whether your sexual soulmate wants to be spanked over a desk or likes to dress up as a giant squirrel. Today, there really is something for everyone.

The doll fetishist

James, 52, civil servant

I suppose you could say that I am a recluse. I've always lived on my own and find it hard to make friends or have happy relationships – I've got a history of unsuccessful relationships with women. I did hope that eventually I would find happiness settling down with a partner and I have tried internet chatrooms and online dating but nothing worked. A few years ago I watched a TV documentary about men who live with "real dolls" (see introduction) and thought it might be the perfect solution as I was extremely lonely at the time. I contacted an online company that makes dolls to order and although I was very nervous about the whole thing they put me at my ease and helped me decide what sort of doll I wanted.

Alice cost me about £6,000 and via the company's website I was able to customise every area of her looks and physical attributes – I admit it seems childish but I got a real kick out of creating my fantasy woman. She's aged about 25 and has dark hair and the perfect body. I also enjoyed being able to choose all her clothes at the click of a mouse; perhaps it's the power thing that appeals – being in control of every aspect of her.

Whe she first arrived, it was a very surreal feeling having this gorgeous and life-like silicone creature sitting opposite me in the lounge.

Very gradually, however, I have got used to having her around and now I have grown to love her as I would a real woman. I know it must seem pretty sad, but for me, she's everything. I think of her primarily as a companion, although obviously she fulfils my sexual needs too – in my experience it's a lot easier and more pleasurable than the real thing! I like the fact that she's always there for me; she eats with me, sits and watches TV with me and sleeps with me. I haven't told anyone about Alice; my work colleagues would laugh at me and if my neighbours saw her they would probably freak out too. To me, however, it's the perfect partnership – and what harm am I doing to anyone else?

The internet sex addict

Simon, 38, regional sales director

I got into internet sex by accident; I wasn't even looking for sex. I was at work about four years ago and a friend was registered to one of those dating sites, and he was having a whale of a time.

He was single at the time and went out on lots of dates with different women and met them once or twice and then slept with them and after that he didn't really see them again. I joined my first internet website for a laugh when I was bored, and I couldn't believe how easy it was to meet up with women. I said I was single on my profile but I was married, of course. I hooked up with one or two girls in the first couple of months but they were all looking for relationships and I wasn't. I felt a bit guilty, to be honest. I was already lying to my wife and I didn't want to have to start lying to another woman as well.

After that I discovered some other specialist websites where married people can contact each other for a bit of flirting and then hooking up. I usually meet the women in a bar first and then maybe we'll go to a hotel.

I spend a fair amount of time surfing the sites, maybe an hour or two a day when I'm at work and then maybe an hour or two at home. I don't think it's excessive, though – people spend hours and hours on Facebook, don't they?

It's not that I don't love my wife or that we don't have sex – we do! But we've been married for 12 years now and we've got small kids and it's not really the same as it used to be. I suppose you might call me highly-sexed. It's just sex, pure and simple. I don't sneak around with the same woman, and I'm not having a big romance behind my wife's back. And I never really have to worry about her finding out because, first, the women I sleep with are married, too – so it's not in their interests to tell my wife – and second, I'm incredibly careful. My wife could go through my computer with a toothcomb and she wouldn't find a thing.

What surprised me about it all was how many women there are out there who were really up for casual sex with someone who's not their husband. I know so many men who say things like, "Oh my wife wouldn't cheat on me," and I laugh and think, OK, whatever, mate – she probably already has, with someone just like me.

The modern Mrs Robinson

Marian, 54, interiors consultant

I was with my husband for 25 years and then he ran off with one of our neighbours and we got divorced. It was quite funny really, looking back on it. I don't miss him at all; it was the best thing that happened to me. But at the time I was really angry and sad.

I kept the house after the divorce and my children were grown-up and I had plenty of money and I sat down one day and thought, "What the hell am I going to do with the rest of my life?" Eventually I hit on the idea of starting my own interiors company, and I was contacted by this woman who was having her whole house re-done after getting a divorce, just like me. We started chatting and she told me about a website where she met young men online for sex. She said it was brilliant and I should give it a go.

So I went online, and within a fortnight I was dating this amazing boy. He was only about 30. He was amazing-looking and wanted to do all the things that men my age just aren't interested in. We went out to the theatre and to the movies and out for dinner and he was just so fun and alive. We saw each other for about three months and then he sort of disappeared, and I didn't mind at all. When I was younger I would maybe have been a bit upset but I didn't give a damn.

When men get into their forties and fifties they don't want to do anything. They just talk about their new cars and sit on the sofa flicking through the channels with the remote. And now I've got so much energy. Ten years ago I felt totally dead, like a zombie, but now I jump out of bed in the mornings. Life is so exciting.

No one believes me when I say it, but going out with much younger men is not just about the actual sex – even though the sex is great and young men these days know much more about it than men my age. The fundamental thing for me is that men in their twenties are a better match for women in their fifties and sixties than men of the same age are. I went on some dates with men my own age after Keith left and all they wanted was a replacement wife to wash their pants. I wasn't having any of that.

I'm seeing a couple of boys at the moment, but nothing serious. And I don't care really. This time in my life is just for me – for as long as I can remember it's been about other people, my husband and my children. Now it's just for me and I love it.

The party animal

Gemma, 23, shop assistant

People think that sex parties are really seedy but actually, they're not. They're much less seedy than most nightclubs, in a way. Firstly, there are so many sex-party swinging sites on the internet, so you can do lots of research in the comfort of your own home. Once you decide to actually go to a sex party, there's no pressure on anyone to do anything; it's usually just a fun atmosphere with people standing about chatting – quite often just drinking tea or something.

I got into swinging, at first, with my then boyfriend Tim, when I took him to a swingers' party in Brighton for his birthday present. He actually didn't enjoy it that much, but I thought it was really fun. The people were nice and there was hardly any drinking or taking drugs or anything like that.

There were living-room areas, where you couldn't get up to anything particularly racy, and then bedrooms upstairs, some with the lights on and some with the lights off, where you could go for more explicit action.

I broke up with Tim about a year later. We hadn't been back to any swingers' parties but I had had sex with someone else at that first party with my boyfriend looking on in the same room and I don't think he enjoyed it; we both realised that we had such different levels of inhibition. I'm not at all shy!

After I broke up with Tim, I went online and signed up for what I suppose you'd call an orgy. It's just the same as a swingers' party, really, except that not everyone is in a couple. It was just really fun. I met so many like-minded people; it wasn't just about sex, it was about being yourself and letting go a bit. There's no pussyfooting around – so if you meet someone and think, "I really like you" and if they like you back, you can just have sex without anyone judging you or thinking you're weird.

I'd never tell my family or some of my more straight friends about this. I don't think they'd get it and there's no point in trying to explain to someone who isn't open-minded what you get out of it. They'd just think I was being a bit of a slag, and I'm not at all.

I don't feel ready to have a steady relationship now. Even if a prospective partner was really amazingly cool, I wouldn't introduce him to the idea of a swinging party because nine times out of 10 he'd be scared off by it.

The asexual

Mark, 44, scientific glassblower

I've always known that I was different from other people, especially when I hit puberty and found that I just wasn't interested in sex in the same way that my friends were. I also found my own gender more interesting and nicer-looking than the opposite sex, so I thought I might be gay. Back in the Seventies, there was still a lot of homophobia.

I started hanging out on the gay scene, which led me to being in bed with people, sometimes men, sometimes women – and I realised that I'm not capable of sex. I just don't get aroused. I did have relationships, but they tended to be very short-lived. I greatly enjoy physical contact, such as hugging, as well as companionship, but unfortunately once people realise that there's not going to be any sex, the relationship usually comes to an end.

My longest relationship was in 1997 with a man. We were together for 10 months and it was a sort of mutually beneficial arrangement whereby he tolerated my affections and I was his ticket to friends and parties. When that ended I thought: this is a pointless pursuit.

My brother, to whom I'm really close, went through a divorce a couple of years ago and I was driving in a car with him and talking about relationships. And I told him. I said, "I'm asexual." And he said, "You lucky bastard!" We laughed so much! I think some people still assume that I'm gay but if they do then it's not an issue. My brother later told me that my parents had asked him more than once if I was gay. I suppose they thought it was strange that I never brought anyone home.

My life really changed when I saw a piece in the paper in 2004 about the differences between asexuality and celibacy – in the former there is no sexual attraction and in the latter a conscious decision is made not to have sex. I saw it and it was a total epiphany. I was so thrilled to find there were other people like me. There's a range of different kind of asexuals – some are born that way (like me) and some become that way over time. At the end of the article there was a reference to AVEN (asexuality.org), the website for the asexual community, and I joined up straight away. When I went to the first meet-up it was a revelation to meet other people who felt the same way as I did. There's always a lot of stuff going on and I've got a busy social life – although I do worry a bit about what things will be like when I get older and I'm on my own.

The adult baby

John, 45, computer programmer

My mother walked out on my family when I was four, so I think I always craved being nurtured by a female figure. My two older sisters and I were looked after by a very strict nanny at our house in Nottingham, who showed us no affection. My father would come home late from work and was of the "children should be seen and not heard" school of thought. My sisters and I spent a lot of time on our own and would invent games where they would play at being nurses and would give me baths, get me dressed and so on.

I have always been quite sexually dysfunctional and my sisters haven't managed to form lasting relationships either. When I was in my early twenties I started a string of relationships with older women and realised that I was fantasising about a mother figure. Things started to spiral out of control when I had strong fantasies about dressing up as a baby – it's called infantilism. At the beginning, being honest about my desires was very hard. I felt like a pervert and didn't know who to turn to. Then I confessed to one of my older girlfriends and she encouraged me to seek professional counselling. My counsellor helped me to understand the root causes for my predilections – a lack of love in childhood – but although she encouraged me to stop dressing as a baby I wasn't able to achieve this.

I then discovered an online adult-babies' club in south-east England where I found like-minded people who wanted, as I do, to dress up in adult-sized baby clothes and behave as a baby might do. This might include being bathed by "nannies", wearing nappies and being "breast-fed". I realise that it sounds weird, but it gives me some sort of comfort at the same time as addressing my sexual needs. The fact that it's all done anonymously through the web provides me with extra privacy, too.