Here's one of boyd's examples, a true story: a young woman, an elementary school teacher, joins Friendster after some of her Burning Man buddies send her an invite. All is well until her students sign up and notice that all the friends in her profile are sunburnt, drug-addled techno-pagans whose own profiles are adorned with digital photos of their painted genitals flapping over the Playa. The teacher inveigles her friends to clean up their profiles, and all is well again until her boss, the school principal, signs up to the service and demands to be added to her friends list. The fact that she doesn't like her boss doesn't really matter: in the social world of Friendster and its progeny, it's perfectly valid to demand to be "friended" in an explicit fashion that most of us left behind in the fourth grade. Now that her boss is on her friends list, our teacher-friend's buddies naturally assume that she is one of the tribe and begin to send her lascivious Friendster-grams, inviting her to all sorts of dirty funtimes.

In the real world, we don't articulate our social networks. Imagine how creepy it would be to wander into a co-worker's cubicle and discover the wall covered with tiny photos of everyone in the office, ranked by "friend" and "foe," with the top eight friends elevated to a small shrine decorated with Post-It roses and hearts. And yet, there's an undeniable attraction to corralling all your friends and friendly acquaintances, charting them and their relationship to you. Maybe it's evolutionary, some quirk of the neocortex dating from our evolution into social animals who gained advantage by dividing up the work of survival but acquired the tricky job of watching all the other monkeys so as to be sure that everyone was pulling their weight and not napping in the treetops instead of watching for predators, emerging only to eat the fruit the rest of us have foraged.

Keeping track of our social relationships is a serious piece of work that runs a heavy cognitive load. It's natural to seek out some neural prosthesis for assistance in this chore. My fiancee once proposed a "social scheduling" application that would watch your phone and email and IM to figure out who your pals were and give you a little alert if too much time passed without your reaching out to say hello and keep the coals of your relationship aglow. By the time you've reached your forties, chances are you're out-of-touch with more friends than you're in-touch with: Old summer-camp chums, high-school mates, ex-spouses and their families, former co-workers, college roomies, dot-com veterans... Getting all those people back into your life is a full-time job and then some.

You'd think that Facebook would be the perfect tool for handling all this. It's not. For every long-lost chum who reaches out to me on Facebook, there's a guy who beat me up on a weekly basis through the whole seventh grade but now wants to be my buddy; or the crazy person who was fun in college but is now kind of sad; or the creepy ex-co-worker who I'd cross the street to avoid but who now wants to know, "Am I your friend?" yes or no, this instant, please.

It's not just Facebook and it's not just me. Every "social networking service" has had this problem and every user I've spoken to has been frustrated by it. I think that's why these services are so volatile: why we're so willing to flee from Friendster and into MySpace's loving arms; from MySpace to Facebook. It's socially awkward to refuse to add someone to your friends list -- but removing someone from your friend-list is practically a declaration of war. The least-awkward way to get back to a friends list with nothing but friends on it is to reboot: create a new identity on a new system and send out some invites (of course, chances are at least one of those invites will go to someone who'll groan and wonder why we're dumb enough to think that we're pals).

That's why I don't worry about Facebook taking over the net. As more users flock to it, the chances that the person who precipitates your exodus will find you increases. Once that happens, poof, away you go -- and Facebook joins SixDegrees, Friendster and their pals on the scrapheap of net.history.

Cory Doctorow is co-author of the Boing Boing blog, as well as a journalist, Internet activist, and science fiction writer. Read his previous InformationWeek columns.