Some people may watch a little television if they wake in the night. Jim Reed of Oceanside, N.Y., reaches for his BlackBerry and posts comments to Facebook.

He goes back on to the social networking site first thing in the morning. And again when he goes out for breakfast and lunch, when he's killing time before an appointment or sitting at a traffic light. He checks it, he estimates, 100 times a day.

Reed, 63, is a retiree, a former Nassau County, N.Y., deputy commissioner and tireless volunteer for organizations and causes. And he has over 1,700 names on his Facebook "friends" list — a tiny slice of the site's membership, which last week, according to co-founder and chief executive Mark Zuckerberg, reached a major milestone: a half-billion active users worldwide.

"It's addictive," Reed said of the site he has used for about three years to dispense congratulations, friendly banter and notices of upcoming events. Nothing very personal, he said, but "it's brought a lot of joy to me."

Reed illustrates the reach and hold now exerted by Facebook, born in a college dorm six years ago as a network for students. Zuckerberg, 26, now sits atop a private company that has doubled the membership it claimed just a year ago. While the majority are young (about 60 percent are younger than 35), the 55-and-older category is one of the fastest growing U.S. segments, up by 922.7 percent, or over 9 million users, in 2009 — and by another 3 million so far this year.

"It added 300 million (active users) in a little over a year and a half and in this day and age with so many options, to be able to do this is amazing," said Sree Sreenivasan, Columbia University School of Journalism dean of student affairs and digital media professor. "They've changed the way that people communicate."

Growth hasn't come without controversy: Concern over privacy concerns in the spring forced Facebook to back away from changes that made more user content public.

But the uproar didn't interfere with Facebook's role as the dominant social network; it has outstripped MySpace and is still ahead of relative newcomer Twitter. It's where friends and friends of friends announce personal news, get messages, post photos, do business, play games, rally for causes, find old classmates and lovers, keep in touch. Time waster or life-changer, for many, Facebook is now simply an unquestioned embed of daily life.

For Barbara Branca, 62, it was a life-changer. She's a poet and band singer who is communication manager for an environmental program at Stony Brook University, and Facebook has connected her to widening circles of poets, musicians, old friends and environmentalists. "I'll be giving three different poetry readings in the next few months because of Facebook," she said. Because of it, she's writing more poetry, and without it, "I wouldn't have had the audience it looks like I'm starting to get."

She added: "I find it's a powerful thing. You can reach a lot of people in a very short time."

But Facebook's appeal goes beyond its utility: It's a place to peer and to preen, a gateway into the lives of others and a platform on which to perform. "You can be a Peeping Tom," said Louise DiCarlo, 49, of Stony Brook, N.Y., who has hundreds of Facebook friends and thousands of Twitter followers. "You don't have to be invited into the house, you can look in the window."

And she can "friend" the kind of people she'd never meet socially.

In terms of Facebook as a platform, "everyone is a journalist, a commentator," said Debra Aho Williamson, senior analyst with eMarketer, an online site analyzing Internet trends for businesses. " ... I think people get a sense of self-worth by seeing how many of their friends notice and comment and like what they post."

She confessed that she occasionally has dreams about her status updates, the pithy posts users write (sometimes several times a day) describing a thought, state of mind, or what's new, that shows up automatically in their friends' Facebook newsfeed. "I wake up in the morning and wonder what I'm going to say about myself," she said.

Facebook's popularity, however, is explained by its utility: for connections, for amusement, and increasingly for business.

Yet even as adults and companies are making themselves at home on Facebook, some teenagers have begun to look elsewhere. Gabrielle, 16, a Locust Valley High School student who asked that her last name not be identified, said she now prefers Tumblr, a micro-blogging network where users can be anonymous.

"Tumblr is more of a private thing where you can post what you're really feeling," she said. On Facebook, "people post what they want people to think of them rather than being honest ... I use it to make jokes with my friends or look at pictures in a group environment, but I really don't use it for anything else. It's kind of tedious. It just gets old."

But Facebook is definitely not tedious to Melinda N. Laterra, 25, although real life sometimes is. Her friends call her an addict for her 12-hour-a-day habit: She is on Facebook at her Northport, N.Y., laundry job, on the train, in her apartment late into the night.

She "chats" with friends via instant messaging, plays games, joins fan pages and groups (over 3,000 of them) including the one titled "I like to turn my pillow to the cool side."

Sometimes, she said, after hours on Facebook she'll think: "I can't look at this anymore, and I'll walk away from it for a little while. Then I find myself wandering back because I'm bored."

Facebook gives her a sense of control. "You can communicate with people at your own limits," she said.

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So Facebook has hit the 500 million user mark — Does that make it social media king? Sure, but it doesn't necessarily mean Facebook is the best option for all our social media needs.

Here's a list of other online tools:

Google Wave

The newest web application from Google allows a group of people to share the same conversation, and link images, maps and video.

Foursquare

Uses a mobile phone's GPS to enable a sort of scavenger hunt among friends in their neighborhood. People can let friends know when they've "checked-in" to places within the neighborhood and their experience.

Formspring

A site where users can ask and answer questions. Want to know what other people think about your new sneakers? Take a photo and ask. Need help deciding who to take to the prom? Let the online world decide.

LinkedIn

Allows users to create a profile of their professional experience to help build business connections. LinkedIn has more than 70 million members in more than 200 countries.

Yelp

A site where people write reviews of places from restaurants to spas and add entries to their to-do list.

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