Somewhere between Facebook and YouTube, the notebook computer became so essential to our lives that we began inviting it to dinner. It came quietly, ingratiating itself into the social ritual with such ease that we barely noticed. Until one night, halfway through the main course, seven dinner companions were suddenly crowded around our unassuming little MacBook watching “Dick in a Box.” What had happened? Once merely a guest, Mr. Laptop had become the guest: the know-it-all who could produce, in an instant, any funny thing that another attendee had read or seen in the previous week, saving that person the trouble of actually explaining it. Not to mention settling pressing intellectual disputes such as, “Who was the bassist in Jem and the Holograms?”

“The laptop is always good for 80’s questions,” noted Michael, 29, a magazine editor living in Chelsea who e-mailed that computers attend his friends’ dinner parties “ALL THE TIME. We often use it to look people up on MySpace and Friendster,” he said. “Like, my friend will say, ‘I met this guy.’ And we’re like, ‘What does he look like?’ And then we all Google him.”

“A lot of times it’s IMDb,” said John Collins, 37, a theater director who lives on the Lower East Side. “You’re trying to figure out who’s the actor in some movie. It’s also replacing wallet photographs. Now people just take out their computer and start a full slide show!”

“One of my friends will be like, ‘So-and-so was on season two of 24, and I say ‘No, she was on season one, I watched every episode,’ so then we look it up to solve the dispute,” said Taja-Nia Henderson, a young lawyer who lives in Brooklyn. “It’s always something ridiculously random.”

‘A One-Upping Thing’

Most of us share intimate relationships with our computers. They’ve become our TV sets, our banks, our photo albums, our encyclopedias, our shopping malls. They make us laugh, and we find them fascinating, just like a good friend. To many of us, the fact that we bring them to dinner is barely worth mentioning.

And yet surely when the laptop comes to dinner, a certain sociability quotient is lost. Like the great democratic equalizer it is, the Internet ensures that you, the party guest, don’t actually have to be funny, you just have to have seen something funny. That you are merely the vehicle for this humor matters little, because the end result is the same: Everyone laughs! As a dinner guest, the laptop is very gracious about deflecting credit onto the person who invited it to the table. Which is, perhaps, why it keeps getting invited back.

Dana Luria, 27, an internship coordinator who lives with her husband, a doctor, on what she calls the “Upper Upper Upper East Side,” said that at her dinner parties, it’s become all YouTube, all the time. “There was definitely the Obama Girl at two or three different dinner parties,” Ms. Luria said. “And then that presidential dinner when Colbert made fun of the president. You know, silly political stuff. I don’t have a job where I’m sitting at a computer all day, so I’ve never seen most of it. But my husband reads Chowhound and Gothamist and all that; he’s always finding things online and showing them to our friends. And then they show him stuff. It becomes sort of a one-upping thing.”

In a more civilized age, it was conversation, not three-minute spoof music videos, that propelled an evening forward, and arguments were resolved by an encyclopedia, or even by polite détente (“We agree to disagree”), which would either be settled in the following days when one or both parties got around to looking it up, or just forgotten in a pleasant post-prandial haze of red wine and cigarettes. “I had a professor in college who said that no dinner party was complete without a trip to the Oxford English Dictionary to check on the precise meaning of a word,” said Lauren, 28, a publicist who lives in Washington Heights. “Of course, we all mocked him mercilessly for this.”

But what would this professor think of Mr. Collins, the theater director, who not only looks up words at dinner, but listens to pronunciations? “I remember having an argument about the pronunciation of the word ‘feral’,” he said. “I thought FEE-ral, and my girlfriend thought FAIR-al. So you go to Merriam Webster online, and you click on the little microphone and a woman’s voice pronounces it for you. I won that one. But it was a case of the computer actually speaking up at dinner!”

In such cases, argue laptop-at-dinner enthusiasts, the computer is an educational tool—merely a way for interesting guests to learn as much as possible from their evening’s interactions. “We had a dinner party on Saturday night, and the laptop was involved,” said Terra Chalberg, 31, a freelance book editor who lives with her boyfriend in Boerum Hill. “We had gone upstairs to the roof and I pointed out a tree with what looked like blackberries on it, but we all know blackberries do not grow on trees, so one of our guests suggested we grab a leaf and a berry and head downstairs to look it up, which he did. I think it was a positive addition to our party.”

Not all hosts are so sanguine about the intrusion of the laptop into the dinner hour. “What I just find so annoying about it is that somebody will start looking something up and then they won’t ever come back to the table,” said one 30-something editor who lives in Fort Greene. “They’ll just sit on the couch with the computer open, checking their e-mail or whatever. Also, you have personal stuff on your computer, so I think it’s sort of rude.”

“A laptop is kind of an antisocial thing,” Mr. Collins admitted. “Say you’re at a table—only one or two people can see it. So it pulls whomever is doing the research out of the conversation. Usually only one other person is interested enough to look over your shoulder. So what was a conversation among five people is now a conversation among two.”

Ms. Luria says she is “really passive-aggressive” when a laptop breaks up her dinner party in this way. “I put a lot of work into making dinner, and it’s sort of deflating when everyone gets up and crowds around the laptop,” she said. “But my husband loves it. He’s always like, ‘Come see this!’ And I’m like, ‘I’ll check it out later.’ It usually happens when everyone’s sitting around chilling and drinking wine, and dessert isn’t served yet. It hastens the end of things. I would never say my friends were rude, but when I grew up, the TV was off during dinner. It’s the same idea.”

‘Catatonic Robots’

What do the experts think?

Peter Post, great-grandson of Emily and author of several etiquette books, argued that laptops should be banned from the main meal, but are fine during coffee hour, when guests linger at the table conversing. “If you’re using the laptop to look something up in the context of a conversation, it’s really no different than going to a dictionary, and we certainly wouldn’t tell people not to do that,” he said. “The mistake would be checking your e-mail. The minute it becomes something personal, it’s the same as answering your cellphone.” A caveat: “Showing friends what I saw most recently on YouTube isn’t the first place I’d go in conversation. It seems to me that that’s starting to cross the line.” If you see one of your guests holed up with his Gmail while you labor to baste the Tofurkey, Mr. Post suggested putting him to work: “You might say, ‘Tom, could you give me a hand with the drinks?’ Or, ‘You’re a fabulous carver, could you help me carve the meat?’ You want him to stop the behavior, but you don’t want to embarrass him in front of the group.”

Thomas P. Farley, editor of Town & Country magazine’s anthology Modern Manners: The Thinking Person’s Guide to Social Graces, drew a harder line. “People should feel free to describe what they saw on YouTube,” he said. “Put it into words. Or better yet, get somebody’s e-mail address and send them the link after the party, when they can look at it in their own leisure time and not when they’re looking to meet and mingle with other people. To bring out a laptop at a party is the lazy way out. It’s saying, ‘Let’s let the computer do all the entertaining for us, and we’re going to sit here like catatonic robots.’”

Perhaps it’s true that the laptop’s presence at the dinner party has made New Yorkers in particular—always famous for knowing it all—a little insufferable. “We’re used to immediate answers now,” Ms. Henderson said. “When I was in college, the Internet had like five things on it. Nobody used it to resolve little disputes with friends. You’d just go home thinking you were right and the other person was wrong. Now we don’t mind stopping everything to find out who’s right!”

And what of personal digital assistants? “I look shit up on my Treo to solve disputes while at Barbuto,” e-mailed a 30-something writer living in Chelsea. “Does not make me popular.” (“Sent from my Goodlink Wireless Handheld,” ended the message, as if to gloat. “Sender is not at his desk. He’s out living!”) Somehow, though, the pervasive Treos and Blackberries seem far ruder than the laptops at dinner. Hosts may barely notice if you spend 20 minutes buried in Wikipedia during the appetizer course. But take out your Treo and text another human, and you’ll get weird looks. You’re allowed to interact with the laptop because it’s there (“my Precious,” is what one television writer calls it, pace Lord of the Rings, caressing his Mac’s titanium contours). But texting people who aren’t in the room is rude.

With a laptop, everyone assumes it’s for the benefit of the group. Hey, you’re about to show them a totally hilarious YouTube sendup by three white rappers in Vermont!

And while we may be ADD-addled know-it-alls, we’re also crammed in rather tightly in this city, and quite often the laptop isn’t so much invited to dinner as it “just happens to sit five feet from the dining room table,” as Ms. Luria lamented. “I mean, if we had an office, nobody would leave the room to go find it. It makes me think I should just put it away when people come over.”

Ms. Henderson agreed, though she was unperturbed by any larger social implications. “The laptop is always in the same room as dinner,” she said. “There’s no physical space between the person looking something up and the rest of the group. I don’t even blink when someone opens it at my house.”