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Facebook is the most popular social network in America — roughly two-thirds of adults in the country use it on a regular basis.

But that doesn’t mean they don’t get sick of it.

A new survey by the Pew Research Center‘s Internet and American Life Project, conducted in December, found that 61 percent of current Facebook users admitted that they had voluntarily taken breaks from the site, for as many as several weeks at a time.

The main reasons for their social media sabbaticals were not having enough time to dedicate to pruning their profiles, an overall decrease in their interest in the site, and the general sentiment that Facebook was a major waste of time.

About 4 percent cited privacy and security concerns as contributing to their departure. Although those users eventually resumed their regular activity, another 20 percent of Facebook users admitted to deleting their accounts.

Of course, even as some Facebook users pull back on their daily consumption of the service, the vast majority — 92 percent — of all social network users still maintain a profile on the site. But while more than half said that the site was just as important to them as it was a year ago, only 12 percent said the site’s significance increased over the last year — indicating the makings of a much larger social media burnout across the site.

The survey teases out other interesting insights, including the finding that young users are spending less time overall on the site. The report found that 42 percent of Facebook users from the ages of 18 to 29 said that the average time they spent on the site in a typical day had decreased in the last year. A much smaller portion, 23 percent, of older Facebook users, those over 50, reported a drop in Facebook usage over the same period.

Facebook’s biggest challenge revolves around figuring out how to continue to profit from its rich reservoir of one billion users — and a large part of that involves keeping them entertained and returning to the site on a regular basis. Most recently, the company introduced a tool called Graph Search, a research tool that promises to help its users find answers on everything from travel recommendations to potential jobs and even love connections.

Lee Rainie, the director of the Pew Research Center’s Internet & American Life Project, which conducted the survey, described the results as a kind of “social reckoning.”

“These data show that people are trying to make new calibrations in their life to accommodate new social tools,” said Mr. Rainie, in an e-mail. Facebook users are beginning to ask themselves, ” ‘What are my friends doing and thinking and how much does that matter to me?,’ ” he said. “They are adding up the pluses and minuses on a kind of networking balance sheet and they are trying to figure out how much they get out of connectivity vs. how much they put into it.”