It's called "25 Random Things About Me." It lives on Facebook, the popular social-networking Web site. It's a list you fill with 25 items of personal information, ranging from the trivial to the intimate.

Trivial: "I hate tuna." Personal: "Part of me hasn't grown past the moment of my father's death." Intimate: "I have been unfaithful, but so far it hasn't mattered much."

You send your "25 Random Things" chain-letter-style to 25 friends, and they fill it out and tag 25 others, and . . .

And soon Facebook - a virtual living room where people hang out and tell everyone else what they're doing and thinking - is awash with personal revelations, admissions, info once kept private.

Facebook turned five Feb. 4. Sometime in mid-January, "25 Random Things" became a wildfire fad there.

Many have called Web lists such as "25 Random Things" narcissism, a word that means egocentrism, with its not-so-great overtones. But Facebook users and experts are saying: Not so fast. Of course, ego is involved. But "25 Random Things" is a product of the information age. And that age is simply different from what went before.

If they are right, "25 Random Things" reveals a decisive shift in our society, and there's no going back. Many of us - younger, mostly - take a distinctive view of private and public, in which a permanent, always-connected audience trades personal, even intimate, information as part of having friends and being social. That hyperconnected life is here to stay. Call this narcissism, but it might be that the train left and you weren't on it.

Facebook spokespeople say that they do not keep statistics on members' activity, but that membership, and the use of "Notes" (where "25 Random Things" lives), spiked last month.

In general, "I really get a kick out of reading" the "25 Things" lists, Nadia Stylianou, 23, a Facebook user from New York, says (via Facebook, of course). "It's usually a test of someone's comedic skills, with a touch of selected personal facts that the person really wants the community to know about themselves."

Marta Abel, 23, of Basking Ridge, N.J., says she likes the lists because "I really enjoy learning about my friends."

Emily Nussbaum, editor-atlarge for New York magazine, says the most decisive difference is that the Facebook generation "assumes they have an audience": They have a mental image of a large group of people interested in postings such as "25 Random Things." Part of their identity rests on an invisible entourage that accompanies them everywhere.

The members of the Facebook generation are right. They do have audiences. This is how they were socialized. "I definitely think I have an audience, because I've always felt cool and popular. And weird. And fun," writes Stylianou: "I think my generation . . . are self-promoters, and a lot of us are narcissistic. . . . [W]e just naturally feel entitled to the fact that we are little celebs in our own minds, and we're sort of casual about that."

Sara Naphas, 23, of Highland Park, N.J., says she "doesn't love" Facebook, and yet she does think she has an audience, especially for pictures: "I think it's a general habit of my whole generation to look online for evidence of the way each other's lives are going."

Aviva Rosen, 20, of Netanya, Israel, says she and her generation think of themselves as living constantly on a stage on which all is shared. "Your [Facebook] profile is like a social circle," she says. "You constantly are connected to everything else, constantly hooked into this separate society that exists outside the real world. Adults may use it as a utility, but to us, Facebook is a whole world. You always have an audience."

Young people are hardly the only ones with that invisible entourage. The businessman furiously inputting on his BlackBerry, that lady serial-cell-phoning on the train - all are connecting with a world of others there in all but body.

That communal aspect is what so much commentary misses about "25 Random Things." It's not just a list; it's a communal exercise. Posters post, and friends comment.

What's that commentary like? An unscientific survey of more than 30 such lists has yet to uncover anything vicious or unkind. Mostly, the virtual community is, in Nussbaum's words, "surprisingly supportive, sweet, even encouraging." It is nurturing, a thing friends do.

Nussbaum says the social-networking generation has come to expect this trade in personal details: "It comes with having a circle of friends." Older users - who have joined in increasing numbers the last two years - initially may find it unnerving, but in time, most adjust to the culture.

Joe Diorio, 53, of Chesterbrook, is one such not-brand-new Facebook-user. He published a "25 Random Things About Me" list recently. How come? "Just for laughs," he says. "I noticed that other people on my [Facebook] friends list had done it. And I wondered whether I could even find 25 random things about myself."

He did. He posted burningly revealing items such as:

1. I became a Red Sox Fan in 1967. . . .

2. Of meeting his wife: She talked to me first; I was too chicken to say anything to her. . . .

9. I was a security guard at a cigarette lighter factory. I worked the graveyard shift and would sit in the guardhouse smoking cigarettes . . . about 50 feet from a 60,000-cubic-foot butane tank.

10. Item #9 proves God protects fools.

Diorio's list is followed by comments from his Facebook friends, often, in turn, commented on by Diorio.

Clive Thompson, contributing editor to the New York Times Sunday Magazine and columnist for Wired, says society is "redrawing the boundary between public and private, and in some respects, it's the most significant intergenerational cultural shift since rock-and-roll. People separated by only five years of age are looking at each other, completely baffled by their behavior."

There are certainly downsides. Christine Rosen of the New Atlantis, "a journal of technology and society," reminds us by e-mail that narcissism is narcissism: "For all of their apparently casual tone, these lists are not filled with random things. They are carefully and deliberately crafted efforts to market their makers as quirky and appealing people. The revelation of one person's quirks can be endearing, but the broadcasting of hundreds of thousands of people's quirks quickly devolves into tedious mass solipsism."

And the social-networking scene can invite and involve true mental problems. In his commentary Monday morning on WHYY-FM, Dan Gottlieb worried about the "delusion" that we must be "always connected." Rightly did he warn: "It is a delusion."

As family therapist Sara Kay Smullens points out, people can fly to Facebook or other sites to avoid their flesh-and-blood family and friends. "It can be a substitute, one that doesn't work, for an intimacy they can't find in real life," she says.

"Random Things" lister Diorio has his own theory about why the lists and commentaries have become so popular. It has a piquant irony: "We spend so much of our lives online with Facebook, LinkedIn, and we spend so much time connected that we feel disconnected. So we tell people these little things, to feel more connected. We put a piece of ourselves out there, to give it a try."

Is there no turning back? Nussbaum says the networked world and invisible entourage are with us forever, "unless somebody pulls the plug, and we're all in the streets, trying to keep our hands warm."

Contact staff writer John Timpane at 215-854-4406