Quora is a Web site that crowdsources answers to just about any question imaginable, including “What is the meaning of life?” and “Is it possible to stick someone to the wall with Velcro?” But anyone searching for a phone number for the company is out of luck. Not only is the number unlisted, but the very question “What is the phone number for Quora?” has gone unanswered for months.


Quora is not the only social technology company that presents an antisocial attitude to callers. Twitter’s phone system hangs up after providing Web or e-mail addresses three times. At the end of a long phone tree, Facebook’s system explains it is, in fact, “an Internet-based company.” Try e-mail, it suggests.


LinkedIn’s voice mail lists an alternate customer service number. Dial it, and the caller is trapped in a telephonic version of the movie “Groundhog Day,” forced to work through the original phone tree again and again until the lesson is clear: stop calling.


Voice calls have been falling out of fashion with teenagers and people in their 20s for some time (text only, please). But what is a matter of preference for the young is becoming a matter of policy for technology companies; phones cost money, phones do not scale. Besides, why call when you can use Google, or send a Twitter message?


On the other end of the line, however, some people may not know how to Google, or do not want to use Twitter. These users may be older, or less technically adept, and they are finding the method of communication they have relied on for a lifetime shifting under their feet. It does not make sense, they say, that a company with products used by millions every day cannot pick up the phone.


The companies argue that with millions of users every day, they cannot possibly pick up a phone.


“A lot of these companies don’t have enough employees to talk to,” said Paul Saffo, a longtime technology forecaster in Silicon Valley. Facebook, for example, has just one employee for every 300,000 users. Its online systems process more than two million customer requests a day.


Google, which at 14 years old is a relative ancient in Silicon Valley, is one of the few companies that publishes phone numbers on its Web site. Its phone system sends callers back to the Web no less than 11 times. Its lengthy messages contain basic Internet education in a tone that might be used with an aging relative, explaining, slowly and gently, “There’s nothing Google can do to remove information from Web sites.”


Google initially tried to handle requests by e-mail, but even that proved too cumbersome. The company now steers incoming questions to online forums.


“All these companies stay away from phone support,” said Mikkel Svane, the chief executive of Zendesk, whose products help companies manage incoming requests. “People get aggressive or aggravated; people are depressed or crying. It’s just hard talking to customers,” he said, adding that these companies have paved the way in large-scale customer service by keeping everything online.


Officials at Facebook, Google and Twitter (all reached first by e-mail) say their users prefer to go online, finding it more pleasant and efficient than wading through a phone tree. But what about other business matters? What if, say, a prospective investor wants to call?


“If people need to get ahold of us, they definitely have sources inside,” said Derek Stewart, the finance director of Foursquare, whose personal cellphone has been mistaken for the company’s main office line. In Foursquare’s offices in New York, phone calls are considered a distraction to the developers and are conducted away from the main work area, in British-style red phone booths, the company’s spokeswoman said, explaining that calls are not part of developer culture.


Still, others see a social cost to this change, a deepening of the digital divide.


“The phone users are getting left out,” said Mari Smith, a consultant who trains businesses in how best to use social media. She should know. Because her consulting company lists an 800 number, frustrated people call all the time, looking for help with their Facebook accounts. She eventually adjusted her phone message to callers to explain that she does not provide technical support for Facebook.


“I just got bombarded,” she said. “They’re just so desperate to reach a real human being.”


Ms. Smith said she believed that large Internet companies might someday return to phones to set themselves apart from competitors. “The ability to call up and get a real human being — the companies who can do that and go back to basics are really the ones that will be winning out and humanizing their brand,” she said.


But for now, some people still feel frozen out when they pick up the phone.


Gabriel McKean, for example, was eager to start using Twitter. His 5-year-old daughter has a rare and painful genetic condition that turns her body’s soft tissue to bone, and the McKeans, who live in Bellevue, Ohio, started a Twitter account for “Ali’s Army” to raise awareness of her disease.


But the account was suspended in a matter of hours — Mr. McKean’s repeated posts of the family’s Web site were quickly flagged by Twitter’s systems as spam.


Upset and confused, he searched Twitter.com for a phone number, but found nothing. He sent an e-mail, but received only automated replies filled with jargon that confused him further. Without other options, he had no choice but to wait for someone to reinstate his account over e-mail.


He hoped to “plead his case” to someone over the phone, but that never happened. Two days later his account was reinstated via e-mail. Given that Twitter handles nearly 400 million messages every day, that might be considered a victory for efficiency and scale, but it did nothing to remove the sting Mr. McKean felt when he could not connect with a real person.


“The plain and simple fact is that they’re too busy or too important to talk to us,” he said.