Before she puts pictures up on her Bebo social networking pages on the internet, Taarna Kim Swanson runs them by her boyfriend. Mostly this is because in some of these photos she isn't wearing all that many clothes. So far, she says, her boyfriend hasn't been concerned, perhaps because Swanson's photoshoots are less about a pornographic sexiness than her alternative make-up and fashion sense. At 18 years old, Swanson, who lives in Fort William, no longer worries too much what her family thinks.

"They've seen my page and, because I'm old enough now, they don't mind," she says. "When I was younger they were quite offended by it: not so much by the way I spoke but some of my pictures which were a bit sexy. I think they thought, Oh no, my little girl's grown up.' In fact, I think they were getting more of a feel of what I was really like."

Among the profiles of other people on Bebo, Swanson's stands out. Not because it is exceptionally raunchy, but because she stares out from her photograph with attitude, winking from under eyebrows arched high. She informs the reader: "Taarna Kim Swanson young mental drunken sexy lies non common sense, self obsessed, attention grabbing, seductive teasing mess." She is frank, in your face, untroubled by punctuation and grammar - and entertaining. Under her "most humiliating moment" she says: "I'm shameless!"

And in a virtual world of attention-seekers, she does catch the eye. In short, her profile seems to embody that which, for a younger generation, is exciting about these sites; but also much of what, for an older generation, is troubling.

Has social networking become the focus of a moral panic? Across the media there are stories voicing concern about how much time children and young adults are spending on sites such as Bebo and Facebook; how highly sexualised their profiles are and the levels of narcissism they exhibit. Social networking sites have been accused of being forums for suicide cults, playgrounds for cyber-bullies and stalking grounds for paedophiles. A recent news story informed us that many teenage kids were producing pictures of themselves with a pornographic content.

Social networking sites ostensibly bar young children from using them, with Facebook, for example, forbidding access by children under 13. Sites also have privacy settings to regulate who can and cannot see users' personal information. However, recent research has indicated that youngsters frequently bypass age restrictions to gain access to the sites and a large percentage of them do not use privacy settings.

Earlier this year, the scientist Baroness Susan Greenfield told the House of Lords of her concern that the generation of children raised with social networking sites may emerge with minds "infantilised, characterised by short attention spans, sensationalism, inability to empathise and a shaky sense of identity". Yet talk to a teenager and they will most likely say, as did one 15-year-old, that it's all an overreaction: "It's just a little fun. You talk to people, meet people. People become involved in more social circles and meet new friends. It's all part of being a teenager."

All of this suggests a new gulf of understanding is opening up between the old and young. A 2007 article by Emily Nussbaum in New York Magazine described this as a revolution akin to the advent of rockn'roll. It forms a line in the shifting sand of how we see ourselves, taking in issues of privacy, how identity is formed and the way friendship is understood. "In the past 10 years," Nussbaum wrote, "a new set of values has sneaked in, erecting another barrier between young and old the older generation has responded with a disgusted, dismissive squawk. It goes something like this: Kids today. They have no sense of shame. They have no sense of privacy. They are show-offs, fame whores, pornographic little loons who post their diaries, their phone numbers, their stupid poetry - for God's sake, their dirty photos! - online."

Stacy Kidd is a 21 year old from Wishaw, and seemingly a little shy. She had told me on the phone that when we met she would be wearing something colourful, but actually she is dressed mainly in black except for flashes of fluorescence. In Edinburgh for the day, looking for a new job, she sits in a café and describes some research she has been doing on social networking for an online magazine. There were differences, she had noted, between how different generations were using the internet. "Older people don't feel the need, generally, to use social networking, because when you're older you're more settled and not looking for new friends all the time. I think younger people are the opposite. They are also trying to form an identity and use the internet for that."

Even Kidd's own attitude over the years has changed, a feature she has in common with most who have grown up with social networking. "You have to be careful and think about what people will find when you start looking for jobs. You hear about employers checking up on your profiles. You never know what someone might be able to find out about you."

One of the major gulfs in attitude between generations seems to surround this issue of privacy. As someone who, as a teenager, put my thoughts in a well-hidden diary, sometimes written in code, I am often shocked by how willing many people are to put similar feelings out there for all who are accepted as "friends" to consume. Kidd's early ventures into blogging included a diary on the networking site LiveJournal. "I wrote the daily stuff that I got up to." As she got older, though, she started to feel that what she had written was "really embarrassing, so I deleted it all". This difficult material was "stuff to do with boyfriends, nothing too heavy".

Even so, Kidd had felt it was safer to write this online than in a paper diary. "At least if my mum was snooping in my room, she couldn't come and find it." For her, writing it was a cathartic experience. It allowed her to express how she felt - and she has this in common with many others online. What seems like a process of advertising their lives is often really part of a writing cure that eases problems.

Swanson was around 13 years old when she first started using Bebo to keep in contact with friends after she moved school. Now she feels that her page on the site is about more than just staying in touch. "It's just about me. When you get a profile page, you can be whoever you want to be and express who you are."

All of Swanson's friends are on Bebo. They started at the same age as her and often draw on her creative talents to help them improve their own pages. "They like the way I write and think I've got good ideas." She says it's the creative element in Bebo that makes it her favourite social networking platform. She likes the way you can change the template of a page using elements called "skins": "I change my skin a lot and I like more artistic skins rather than those that express how I'm feeling." She says you can read a lot through other people's skins. "People use them so that everyone else knows how they're feeling: if they're upset or jealous. Most people have real attitude ones or bitchy ones."

The Bebo culture is increasingly "lookist". Indeed, most of the activity on there seems to be about adding and commenting on photos. This is a move that Kidd, who started in the older, more text-based, days has found troubling. "I think nowadays a lot of it is focused on looks," she says. "With my younger sister and my friends, a lot of the groups they are part of are basically about people taking photos of themselves. It's really vain. I think, why are all these people posing for photographs? I didn't do that. I don't know anyone who did."

On the surface, social networking profiles can look like a chaotic jungle. But there does seem to be some sort of underlying etiquette. So what were the rules that those I interviewed could identify? Many users are critical of, as Swanson put it, "girls that are really bitchy on it and cause conflict". And almost everyone I talked to argued that being "real" and convincing was paramount.

Much appreciation went out towards those who were boldly honest; there was disdain for those that were perceived as fake. Swanson says she tries to come across "just really how I am". For her, the important thing about a page is "how you come across and if you are for real on it".

The result of this keep-it-real etiquette is that many of the female profiles seem like pages from teen magazines, littered with star-sign descriptions, messages of self-help wisdom and quizzes that are designed to reveal elements of a person's character. Reading them is like stumbling upon a moment-by-moment document of the process of growing up. It is here, among these virtual outfits, that many teenagers and young adults are finding their way to who they are.

The idea that the internet can broadcast and hold on to your mistakes, careless comments and emotional outbursts does not seem to trouble this generation. As Swanson puts it: "What I say is basically how I am at that time. What I put down is basically how I feel, so I don't ever regret that."

Almost everyone, though, was able to recall a time that they had put something up they then regretted. According to 19-year-old Hollie Burns from Troon: "It's very easy when you fall out with someone to have a rant on your page, and the next thing you know everyone knows and you think, I should have kept my big mouth shut'."

Some parts of the media give the impression that a generation is growing up to see the internet as its primary form of communication, and is losing the habit of person-to-person contact. Mostly, however, this is not the case. Social networking sites are generally being used not as a replacement for one-to-one physical exchange but as an addition to it. Kidd, for instance, says that if she had a problem to talk about she would rather see someone. "I'd rather talk face-to-face than even on a telephone. That maybe wasn't so much the case when I was younger. But it is now."

One of the sources of this confusion lies in the use of the word "friend". Many of those who are not involved in the culture fail to understand that users know full well the difference between those social networking contacts known as "friends" and true friends. Most, in fact, are very clear on this: Burns, for instance, accepted 2000 friends to her page, but estimates that only 70 of them are real friends. Most are just people who had been added because they wanted to look at her page. For her, the difference is easy to explain: "You can pick up the phone and phone a real friend with your problems. Bebo friends are just there to talk to when you're bored and your real friends aren't online."

Online friendship is a political minefield, though. Who you befriend, who you list as a "top friend", whether you stay friends with an ex or block someone you have fallen out with - all of these are difficult to navigate. Josh Wilson, the 23-year-old editor of a gaming magazine, recalls that his father recently asked to be his Facebook friend. "It took me about three weeks to accept because I wasn't sure. I changed my profile picture first. I think he just did it because he found us on it. I couldn't not add him as a friend."

So is there really a generational gulf? Or is it rather a gap of understanding between those who embrace the technological platforms and those that don't? "I think it is true that there is a difference in attitude between generations about what privacy means and how it is valued," says Kidd. "But there are exceptions in all age groups. I know people who are my age or younger than me who don't have any sort of networking profile. They don't want it."

Kidd points out that there is even a chasm between her and her sister, just six years younger, in their approach. "My sister will sit for hours and I'll be like, What are you doing on there all that time?' I don't think it's good, the habit of sitting and commenting on people's photos and just uploading things or changing your profile."

The American academic Danah Boyd believes that those who are sounding the alarm are coming to conclusions without truly understanding how social networking sites are being integrated into people's lives. She believes, for instance, that Susan Greenfield's fears surrounding the child and the teenage brain "are driven by a misunderstanding of youth engagement with social media". As Boyd puts it, teens aren't doing anything so very different on these networks than they might have done in previous times. "They're hanging out. Although adults often perceive hanging out to be wasted time, it is how youth gets socialised into peer groups." She notes that many adults worry about the amount of time young people spend online but says: "Most teens would agree. It's not the technology that encourages youth to spend time online - it's the lack of mobility and access to youth space where they can hang out uninterrupted."

In a sense, when you glance inside the world of these profiles, what you catch is a glimpse of youth space. You see what teenagers are doing out there in a space where they think they aren't being watched by adults. And this is the source of some of the panic: never before have we had such access to the intimate thoughts and behaviour of youth, and we are shocked, having long forgotten our own bumpy passage through these years. But if we don't like what we see, we should worry less about the technology and more about what underlying social factors are driving the behaviour we find there. Indeed, Boyd suggests that, rather than clamping down on the places and spaces in which teenagers and young people can experiment, we need to look a bit more closely at what is behind this narcissism. She blames an educational culture of over-praise, combined with a lack of outlets that create real self-worth.

"Eliminating MySpace will not stop the narcissistic crisis that we're facing," she says. "It will simply allow us to play ostrich as we continue to damage our children with unrealistic views of the world."