Young people have a very different attitude to online identity
An employee who forgot their password to log in to the corporate network would probably get a withering look from the support staff as they grovelled to have it reset.
By contrast it seems that young people who forget their MySpace logins are just as likely to make a new account as fret over their lost friends or painstakingly constructed homepage decorations.
I've seen this myself with my daughter, who has been through more user accounts, social sites and e-mail addresses than I could even begin to keep track of and seems to see nothing unusual in abandoning a profile because it doesn't feel right any more.
Recent work by US-based social media researcher Danah Boyd, one of the more astute observers of network behaviour, indicates that it is a more general attitude.
Her observations of young net users have led her to believe that "many teens are content (if not happy) to start over with most of their accounts in most places", and she has noted that for young people an online profile is "not seen as something to build an extensive identity around, but something to use to talk to friends in the moment".
She was particularly impressed by the kids who start a new profile simply because they can't remember their login name or password.
It isn't an attitude I share, perhaps because I'm less willing to spend time setting up new accounts but also because I work hard to manage my online presence and to present a unified identity wherever I happen to be logged on.
Not all young users are casual about their online identity, of course, and Boyd is at pains to point out that many young people invest heavily in aspects of their online activities. However, the willingness to abandon a profile as a work-in-progress and start over is definitely something I've observed in my children and their friends.
Nor is it a new phenomenon. When my daughter was younger she was hooked on Neopets and had five or six accounts going at the same time, partly because she could then trade with herself and game the system but also because she expressed different aspects of her personality in the different accounts.
This approach to online identity has a number of implications for anyone trying to understand the way the internet is growing, and also carries an important lesson for those trying to build services or make money out of them.
One positive aspect is that it will make it harder to pin online activity onto a real person, since accounts that are created and quickly discarded will contain fewer identifying details.
More importantly, this casualness clearly renders any statistics about the number of signed-up users effectively meaningless, and this could be a big problem for the sites themselves as companies vie for investment and point to sign-ups as an indicator of popularity and future success.
Commentator Clay Shirky has been waging a campaign against the sloppy journalism of those who quote Linden Labs figures for Second Life "residents".
He points out that many happily accept the headline figure of two million users without considering that only 36,000 of those are paid-for accounts while a high but indeterminate proportion of the remainder are inactive, set up for free by people who tried out the service and then moved on.
It is the same with MySpace, Bebo or any of the other social sites, of course, and shows how poor we are at measuring what really goes on online.
Websites, having struggled for years to adapt to the idea of the pageview instead of the server request as the key measure of site activity, are now building interactive pages that occupy user attention and time but don't generate hits or page views - and they don't know how to measure this usage.
It may just be that I'm older and therefore more boring, or it may be that I simply have less time for that sort of thing, but there's a part of me that wants a way to match online identity with real-world identity in a solid, straightforward way.
Organisations like the Liberty Alliance offer tools for managing online identity that can limit the information we share with other people and still prove who we are for the situations where assured identity is absolutely vital - like when dealing with a bank, or getting academic credit for an online course.
But there are many other areas of life online where the fluidity of non-identity, of the carnival mask and the assumed name, are also vital, and not just for furtive encounters in chat rooms.
I had always thought that this would involve carefully-chosen pseudonyms and some sort of identity management system, but the answer seems to lie in throwaway accounts and a far more casual approach.
As with so much else about the digital world our kids, having grown up with this stuff all around them, seem to be finding ways to make it work for them that escape those of us who will always be digital immigrants. But at least we can learn from them.
Bill Thompson is a regular commentator on the BBC World Service programme Digital Planet