Not long ago, Schuler and his boss, Robert Pittman, got to talking about feeling enslaved by e-mail. They decided that one antidote might be to institute companywide e-mail-free weekends: If you don't have a piece of pressing business, you are encouraged not to log on at all. Of course, Schuler sees most of his business as pressing, so he rarely abstains. When VH1's Zalaznick had her second child two years ago, she found that nights afforded an unexpected opportunity. "I'd get up at 3 or 4 a.m. each night to nurse my baby," she explains. "In the peacefulness and bondingness of it all, I'd find myself holding her in one arm while reading and typing e-mails with the other."

In the emerging e-mail etiquette, a great deal is sacrificed in the name of efficiency. "E-mail may be the rudest form of communication yet invented," says Nathan Myhrvold, until recently the chief technology officer at Microsoft.

E-mail eliminates tone of voice, body language, and the sort of social cues and contexts that make it possible to distinguish between different messages intended by the same words. In technological terms, e-mail has a limited emotional bandwidth. Because messages are typically written quickly and in compressed form, it's scarily easy for misunderstandings to occur. An abbreviated response that would fly smoothly in conversation can be read as brusque or dismissive in e-mail, partly because no greeting or sign-off is expected. And even highly literate people feel free to send e-mails filled with typos, spelling errors, incomplete sentences, bad grammar, and no capital letters or punctuation at all.

Of course, it plays both ways. The same breezy informality that frees people to be curt, sloppy, and rude in e-mail also promotes a certain openness and intimacy not encouraged by other forms of communication. NYU's Sproull refers to it as a "disinhibiting" effect. "It's not unlike what happens when people put on masks and Halloween costumes," she explains.

"I am much more intimate and personal in e-mail than I am anywhere else," says Barry Diller, chairman and CEO of USA Networks. "That may be just because everyone, including me, is all closed off and constipated, but whatever the reasons, there's a real value to it. In talking, my cognitive process is instinctive and reactive. With e-mail, the process is primarily written. I have to focus on what I'm going to say, compose sentences, make myself understood, reflect before I react. I might be just as tough in writing as I would be verbally -- but then I read what I've written and edit myself."

Nathan Myhrvold has had just the opposite experience. With this loosening of inhibitions, he says, comes a certain rashness -- a tendency to act out. "Just because you have a little more time to reflect with e-mail doesn't mean you do," Myhrvold argues. "E-mail emboldens people. It makes them more extreme. There's something cathartic about pushing the send button, even when you're sending something you may later regret."

The instant intimacy fostered by e-mail is not unlike the exchange you might have with someone in a bar late at night after a couple of drinks, when even the most revelatory exchanges somehow don't fully count. "E-mail relationships are a way to bond very quickly," says Zalaznick. "You don't have to spend much time on them. They're safe. And you can bail out at any point without significant consequences." That's also precisely their limitation: Real engagement is messy, time-consuming, and exacting in a way that e-mail is not. "E-mail is sort of deadening -- a little bit like turning Technicolor into black and white," says Arlie Hochschild, a professor of sociology at the University of California at Berkeley and author of Time Bind: When Work Becomes Home and Home Becomes Work.

One of the ironies of e-mail is that it can be so isolating. "When you log on, you feel like you're in touch with everything that's going on in the world," says Judith Regan, publisher of Regan Books. "But what you really are is out of touch -- literally. There is no touching anymore. We started this century with small communities and large families and neighbors visiting each other. We're ending it alone in a room with a joystick." As it happens, Regan herself is so busy that I've only been able to catch up with her by calling on a Sunday morning. "This is a perfect example," she says. "Here I am, sitting at home in front of my computer answering e-mail at ten in the morning when I should be in bed with a handsome guy making love."