At first, Rod Buchignani just circled Facebook, eyeing it with curiosity, wondering if he should partake.
He joined last year, but the 64-year-old Northern Californian kept the social networking site at arm's length, thinking it belonged to younger generations.
"I wanted to get a flavor of what it was all about," he said. "It didn't appeal at the time, because there were a lot of younger people, and I didn't do too much with it."
My, how times have changed.
Now, about a year later, as more of his friends and family have joined, Buchignani shares photos, posts updates two or three times a week and regularly exchanges messages with other members.
"I feel like he's on it more than I am nowadays," said his 21-year-old daughter Claire.
Although it started as a college site, restricted to only those with ".edu" at the end of their e-mail addresses, Facebook has grown into a mammoth social mainstay. Facebook has publicly acknowledged that it has graduated well beyond its roots, revealing that the fastest-growing demographic is those 35 years old and older.
But new data suggest Facebook could be even more mature than previously believed.
According to the digital marketing firm iStrategyLabs, the number of users 55 years old and older grew about 500 percent in the last six months alone. Using demographic estimates disclosed by Facebook to advertisers, iStrategyLabs determined that the 55+ crowd could soon overtake high schoolers.
Out of the nearly 72 million Facebook members in the United States, as of July 4, the marketing firm said about 5.9 million are 55 years old or older, while about 7 million are 17 and younger. And in the same time period that saw remarkable growth for the oldest demographic, the youngest demographic grew by just 24 percent.
Peter Corbett, CEO of iStrategyLabs, acknowledged that part of staggering growth came from the fact that the older demographic started from a much smaller user base. But he believes the political and economic climate had a hand in propelling the growth.
"Facebook played such a large role in this election," Corbett said. Hearing it mentioned by news organizations, activists and party leaders time again likely led them to wonder, "What is this Facebook thing? Why is everyone talking about it?" he said.
"Then compound that with the economic environment," he said. People out of work might have felt the need to stay current while looking for opportunities, he said, and those still employed might have been compelled to stay connected with peers to secure a safety net of opportunities in case their luck changed.
As the demographics of Facebook shift, he pointed out, the dynamics of families, friend groups and work environments are shifting as well.
Aside from the estimates it provides to advertisers, Facebook does not publicize raw data on user demographics. And some have said that because user data fluctuate over time, comparing information from two dates doesn't necessarily present an accurate picture.
"Facebook has more than 200 million users around the world and we continue to see growth in all age segments, including people over age 55, in high school and college," Facebook spokeswoman Brandee Barker told ABCNews.com in an e-mail.
But other analysts say iStrategyLab's report is consistent with trends they've observed.
"I think that Facebook has pretty much reached a saturation point with young people. There just aren't that many more young Internet users out there who aren't on Facebook," said Debra Aho Williamson, a senior analyst with New York City-based research firm eMarketer.
She said it makes complete sense that Baby Boomers and Gen X-ers would be growing more substantially than other demographics on Facebook.
"It really represents to me that the way people are communicating -- not just young people -- is changing," she said.
Keith Loomer, a 56-year-old from North Conway, N.H., has been at the Facebook way of communicating for only three weeks.
After hearing about it from friends, he decided to see for himself what the buzz was all about. For him, Facebook has been a nonstop walk down memory lane.
He's accumulated a couple dozen friends (though he said "he's gaining them all the time") and those digital connections have stirred up memories of places he hasn't lived for years.
"It seems like when you get to a certain age, you start looking back at where you came from," he said, adding that he's had the most fun finding old friends -- even old girlfriends -- on Facebook.
"The amazing part is how people change. Everyone gets older, but you don't realize how old you've gotten until you see everyone else and go 'wow.'"
Beverly Meyer, a 61-year-old from San Francisco who joined in February, said it started as a way to share photographs but has ballooned into much more.
"It's kind of like going down the rabbit hole for Alice in Wonderland," she said. The more time you spend on it, the more it reveals its potential."
After about five months on the site, Meyer updates her status when inspiration strikes and uses it to keep in touch with far-flung friends from Greece to the United Kingdom to India.
Like others, she's found old friends and classmates. One childhood friend, with whom she had a falling out about three years ago, used Facebook to extend something of an olive branch and reconnect, she said.
Those who have been on Facebook for longer have an even more intimate relationship with it.
"To me, Facebook is like my sidekick," said Melinda, a 57-year-old New Yorker who asked to withhold her last name to protect her privacy. Daily she takes in the wisdom of the crowds, reading friends' updates and queries, and often contributes comments of her own.
For her generation, she believes Facebook provides companionship, optimism and maybe an escape from the foibles and frailties that emerge later in life.
"It's more than a playground. It's like going back to school -- to the community you had in the dorm," she said. And though that regression to a more juvenile time can also ignite more juvenile fears (who hasn't worried at least once that a fellow Facebooker might reject your invitation for friendship?), she said the difference is that online you are only as vulnerable and exposed as you want to be.
"You have a lot within your control, and I think ultimately that's a big thing for people over 55," she said.
But though boomers and those older say Facebook is good for them, some have asked if they are good for Facebook. If marketers want younger users who are still establishing their brand preferences, analysts wonder what happens if older members drive them away.
"Is Facebook going to be the frat party after the last keg has run dry?" asked eMarketer's Williamson, voicing the argument she's heard bandied about.
But though younger users are known for their fickleness, Williamson said this hasn't happened yet and she doesn't expect it to happen soon.
Rob Enderle, an independent analyst, said it depends on how Facebook manages the different demographics and customizes their experiences.
"If you can segment the demographics and serve both groups, it isn't a problem," he said, pointing out that Facebook has recently started to move in this direction by giving users the ability to assign friends to different groups depending on the nature of their relationship (personal, professional, familial, etc.).
At some point, he and Williamson expect Facebook to equip users with tools to send out (and restrict) communications based on these groups. For example, a picture from a college reunion would go only to college friends while a message about a work event would only go only to professional contacts.
"I'm not seeing people abandon Facebook," Enderle said. "Once you put a lot into it, you don't want to duplicate that someplace else."
And though much has been made about young members worrying that their parents might friend them to spy on them (a Facebook group, "For the love of god -- don't let parents join Facebook" exemplifies that fear), many parents and users over 55 say they joined precisely because their children or younger relatives asked them to.
Debbie Donaldson, a 57-year-old from Sonoma County, Calif., said she joined about a year ago at the behest of her 23-year-old daughter.
"My initial reaction was this is just for kids," she said. "But my daughter said there's more of a sophistication to it."
Now she uses Facebook regularly to keep up with her daughter and her friends, and to reconnect with her own friends and former classmates. But she joked that older folks have a tougher time finding friends for one key reason: Hoping to hide creeping wrinkles and added weight, "the old people, they're not putting their pictures on their pages."
Though Donaldson enjoys the online interactions with her daughter, being her "friend" on Facebook is not without its complications.
Although she'll comment on pictures posted by her daughter and her friends, she said she's very careful about what she says.
"I don't want to sound like I'm one of them," she said. "I don't want to be less of an authoritarian than I am."
Another parent, who asked to remain anonymous, raised similar concerns about the new "etiquette code" on Facebook.
When you friend a child's boyfriend or girlfriend and they break up, do you automatically un-friend the ex? Or, if your child un-friends a mutual friend after an argument, do you also remove the friend out of solidarity or remain neutral and do nothing?
For their part, the children of these older users acknowledge that finding parents -- and in some cases, grandparents -- on the site has been a bit surprising. But they also recognize that the site itself is still evolving.
"When he first joined, of course it was a little odd," said Claire Buchignani about her father's foray onto Facebook. "It was my dad on Facebook, and originally it was just for students."
But, she said, "I think that there's definitely enough room for all of us."