GOSSIP HAS LONG had ferociously bad press. But the major rap against it, that it is trivial, is no longer the main thing to be said about it, if ever it was. For gossip has come to play a larger and larger role in public life in ways that can thrum with significance and odd side effects.

Until the invention and widespread use of the Internet, gossip could be conveniently divided between private and public spheres. Private gossip, the engine of English novels from Jane Austen to Barbara Pym, is largely restricted to include friends (and enemies) and acquaintances. Public gossip, which has been around since the printing press, is about people who appear in print or on radio or television, broadcast for the titillation of the larger world. To qualify for public gossip, one formerly had to have achieved some measure of fame or notoriety. But with the advent of the Internet, one can arrive at notoriety without having first achieved anything. And like the distinction between gossip and news, that between the private and the public has become blurred in the digital age.

"The Internet," writes legal scholar Daniel J. Solove, "is transforming the nature and effects of gossip." In his book The Future of Reputation: Gossip, Rumor, and Privacy on the Internet, Solove recounts the story of an insensitive remark that appeared online, supposedly spoken by the clothing designer Tommy Hilfiger: "If I had known that African Americans, Hispanics, and Asians would buy my clothes, I would not have made them so nice." Hilfiger is also supposed to have confirmed that he made this most impolitic remark on Oprah, causing Ms. Winfrey to throw him off her show and tell her audience not to buy his clothes. The effect of this caused Hilfiger's business to slump drastically. The problem is that Tommy Hilfiger never made the remark, nor had he ever appeared on Oprah. But the story was out there in cyberspace; you will find it is still out there today.

Solove tells the story of a girl in South Korea who refused to clean up after her dog on a subway. A fellow rider with a cellphone camera caught her in the act of refusal and passed it along to someone else, who put it on his blog. A man with a much more popular blog picked it up and put it on his site, and from there it took off, so that the girl became known around the world as the "dog-poop girl." She was henceforth harassed, as was her family, and because of it she eventually decided it would be best to drop out of the university she attended. The moral here isn't that you should always clean up after your dog, even though you should, but that you never know who's watching, and if it's the wrong person and he has a phone camera and a friend with a blog, it can mean serious trouble.

Not long ago in the Style section of the Sunday New York Times, a young woman wrote a letter to an advice columnist saying that she had recently broken up with her boyfriend, who wrote about the breakup in his blog in a way that made her look bad. The problem is, as she notes, if a prospective employer decides to search for her name on Google and discovers all the terrible things her ex-boyfriend has said about her, it could — more than could, it is likely to — be damaging to her chances of getting the job, not to speak of getting future boyfriends.

THE INTERNET HAS been splendid in the freedom it has given people to express their opinions, in catching out politicians in egregious lies and journalists in shoddy practice, and in so much else. But it is the other side of that freedom — the freedom to libel, to invade privacy, to wreck lives — that has gotten so little, though greatly needed, attention. Professor Solove remarks that the Internet is, historically, in its adolescence — and it is precisely as an adolescent that it now tends to act: wildly, thoughtlessly, destructively. Lars Nelson, of the New York Daily News, has called the Internet, in this aspect of its young career, "a vanity press for the demented," and this is more than an amusing phrase.

Solove tells of a young woman working in the office of a U.S. senator who published a blog in which she blithely set out the details of her sex life. Her activity was frequent, and the details she supplied were copious, including the oddities of the appetites of the men with whom she bedded down. This man preferred only anal sex, that one had a taste for spanking, another gave her money for sex — that sort of thing. Soon enough her blog, originally meant only for a few of her friends, was picked up by a Beltway blog called Wonkette — itself known for its bawdiness — which had a larger following, and presently the young woman's name and the details of her sex life were broadcast much more widely than she claims at first she intended.

The strangeness of the story is that the young woman didn't seem to mind the publicity. She rather liked the notoriety it brought her. "Public embarrassment," she wrote, "is really very liberating. You really stop caring about what people think, which is something only the elderly seem to be able to accomplish with great aplomb. So I am way ahead of everybody. And those of you behind me can kiss my ass."

Some of the men she wrote about felt much less at ease with public embarrassment than she, and at least one, who argued that he was readily identifiable in her blog, sued her for invasion of privacy, claiming "severe emotional distress, humiliation, embarrassment, and anguish." Hard cheese on him, as the English say. The young woman, whose name is Jessica Cutler, flourished, at least as we understand flourishing in contemporary life. She was interviewed and photographed naked by Playboy; she wrote a novel called The Washingtonienne (the name of her blog), for which she is said to have been given a $300,000 advance; and she eventually married a bankruptcy lawyer with whom she has had a daughter. No business like blog business, at least for some.

MALICE IS ALSO too often an element of gossip, and the Internet, in this connection, can be a powerful aid to malice, by spreading falsehoods — or even harmful truths — with a speed undreamed of by small-town over-the-back-fence gossips. Sometimes not even malice is required for the Internet to do its job as an engine for gossip. Things are mentioned on one blog, picked up by another, linked by a third to two others, and soon something meant to be strictly intramural becomes global.

Gossip has its good qualities, in supplying important information not available in any other form, and its destructive ones when motivated by meanness and the intent to bring a person down. The Internet, it turns out, also has a vigilante, or posse, function that is an arm of gossip. In this respect, you not only accuse a person of wrongdoing, but also join forces with others to round him up, as in the case of the poor dog-poop girl.

Blogs exist, among other things, to shame people who fall below what are thought to be proper standards of behavior, in which the people who do so are named for anyone to see. I learned from Professor Solove's book that there is a blog called BitterWaitress, which names poor tippers on what it calls the Shitty Tipper Database, or anyone who leaves tips of under 15, or in some cases 20, percent of the check. The best-selling writer Malcolm Gladwell found himself named on this blog, though he claims not to recollect ever undertipping. But once his name appeared on the list, his claims counted for nothing.

Another such blog is called Don't Date Him Girl, which lists men, and their profiles, who in their relationships with women have been disloyal, sexually aggressive, liars, mama's boys, and any other information that is useful in condemning these men. All this information may be quite true — men, as I am fond of telling my granddaughter, are brutes — but what if some of it isn't? What if some of the names are placed there because a woman feels falsely betrayed or is herself psychologically off-kilter or is seeking revenge for a man's not finding her attractive? In Don't Date Him Girl and other such blogs, the old question arises: Who is guarding the guardians?

The blog, with its absence of face-to-face contact, provides something very like whiskey courage — cyber courage, let us call it — and it cannot be a good thing. In its destructive aspect, gossip is about two things: the ruination of reputation and the invasion of privacy. No institution does these two things more efficiently than the Internet, where gossip can be menacing and will remain menacing until the time when laws come into being to guard against its many excesses. It's difficult even to think about the complexity of such laws, which would require guaranteeing both freedom of speech and protection of reputation and privacy. But the need for them is becoming more and more acute, as became evident when, in 2010, an 18-year-old student at Rutgers University, after two classmates photographed him with a webcam having sex with another male student, took his own life.

As far as I know, I have never been directly gossiped about on the Internet. I live, after all, a dullish life that does not provide much fodder for exotic gossip. But I have been insulted innumerable times online, as has anyone who writes for the general public, and insults not made to your face but with the capacity to be instantly widespread are an indirect form of gossip. Stendhal said that to write a book is to risk being shot at in public. But until the Internet, one didn't know all the tender places in which one could be shot. And there is no redress, not really, not likely, not ever, not so long as the Internet remains the playground of the too often pathological and the Valhalla of the unvalorous, where the unqualified and the outright foolish can say what they please about whom they please, which in the end amounts, as Molly Haskell has it, to "democracy's revenge on democracy."

Meanwhile, until such time as laws governing behavior in cyberspace are made, or at least an etiquette for Internet behavior is developed, we are all potentially Internet victims. So clean up after your dog, never leave less than a 20 percent tip, be more than attentive and courtly on dates, do not divorce or break up with a partner....In fact, maybe you'd do better never to leave your apartment, what with all those little Big Brothers and Sisters out there watching you.

Excerpted from Gossip, by Joseph Epstein. ©2011 by Joseph Epstein. Reprinted by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.