Darwin Bebo

A bear flag flies over the Castro the weekend of the International Bear Rendezvous

The lobby of San Francisco’s stylish Parc 55 Hotel was packed with bears. Not beasts from the forest, but large, hirsute gay men in jeans and hoodies.

The men gathered for the International Bear Rendezvous last month, lounging on red Barcelona chairs and hugging near the elevators. Over the last 17 years, the event has attracted thousands of grizzly men and their admirers from around the world.

But this year’s festivities marked a bittersweet finale — the bear event is now extinct.

“I’m sad,” said Darwin Bebo, an event organizer for the past nine years, noting a lack of volunteers and a decline in registrations — to 550 this year from nearly 1,000 in 2006. “They’re already talking online, so they don’t need a club.”

Bebo blamed the Internet. As online social networks have surged in popularity with gay men and lesbians, many social groups have been in decline.

The tug of war between the virtual and physical worlds is happening in every stratum of society, but in the gay community the shift has been especially poignant and with significant implications. Social groups helped start the gay civil rights movement, and in recent decades they have raised millions of dollars for causes like same-sex marriage and the battle against HIV/AIDS.

This has left some wondering, as social groups wane, who or what will pick up the rainbow flag.

The Men’s Associated Exchange, a club of professional gay men, disbanded in 2009 after 21 years and a membership that had once reached about 1,000. A final statement on the group’s website read, “As the Internet grew and provided other avenues for socializing, it was time to give in to the new social networking that had become so popular.”

Last month another social group, the Academy of Friends, scaled back its annual Oscar Night fundraiser, which had once attracted an upscale crowd of 2,500. This year’s event was moved to a smaller venue with 1,500 attendees.

“It has been very challenging for us,” said Jon Finck, an Academy of Friends board member. In the last 31 years the group has raised more than $8.5 million for HIV/AIDS charities, but the downsizing of Oscar Night meant less money for those groups. “It has made those payments not as robust as we would like,” Finck said.

The recession played a role (tickets for the Oscar event start at $250), but Alan Keith, the group’s chairman, said that in recent years the group has also struggled to attract new participants, especially younger ones: The board of directors has dropped to 19 members from 29, with only two under 30 years old.

Keith said many gay and lesbian groups were currently reassessing, asking, “What are the needs of our community?”

The roots of many gay and lesbian social groups date to when homosexuality was a crime and gatherings were illegal.

“Social groups and networks founded the GLBT community as early as the 1950s,” said Paul Boneberg, executive director of the GLBT Historical Society. “It represented an ability to find each other.”

“Their newsletters were the first gay publications,” Boneberg added, citing groups like the Daughters of Bilitis, founded in San Francisco in 1955.

New technologies have usurped that role, sometimes serving remarkably narrow niches. The bear community, for example, has Scruff, an iPhone application that instantly locates others nearby, using GPS. There is also the new Web-based startup Bearbook, which works like Facebook except that a membership fee allows bears to see each other, uh, bare.

“You see a lot of proving grounds disappear with the advent of the Internet,” said Don Romesburg, assistant professor of women’s and gender studies at Sonoma State University. In addition to social groups, Romesburg said, gay bars and neighborhoods across the nation have also diminished.

But Romesburg warned against judging the trend as generational, noting that as a gay man, “people my age — I’m 40 — are opting out of these too.” Additionally, he said, more welcoming attitudes toward gay men and lesbians had reduced the need for cliques.

But struggles involving same-sex marriage, discrimination and AIDS continue. The bears raised more than $600,000 over the years for those causes, and it is unclear what will replace their effort.

Boneberg said he thought such efforts would continue, just “in a different way.”

“I don’t see the transition as a weakening of the community,” he said. After all, people might be meeting these days in the cloud, but they do eventually come back down to earth.

This article also appears in the Bay Area edition of The New York Times.