The world's largest social networking site, Facebook (www.facebook.com), recently celebrated its 10th anniversary, which calls for a look backward and forward. 

Founded in 2004 by Mark Zuckerberg and four of his Harvard University classmates, Facebook was initially limited to Harvard students before first expanding to other colleges in the Boston area, then other Ivy League colleges, then other colleges, then high schools, then anyone in the world who claims to be at least 13 years of age. 

Today Facebook contends it has more than a billion active users, about one-seventh of the world's population, though this number is likely exaggerated. Still, the reach of Facebook is undeniable. CEO Mark Zuckerberg's stated goal is to "connect the world." Part of his recently announced 10-year plan is helping users "answer interesting questions or solve problems." 

People use Facebook to keep up with news about friends and family, write public and private messages, post photographs and videos, find people from their past, and join common-interest groups organized by workplace, school, hobby, or other characteristics. 

New media Facebook received its most splashy old media attention with the release in 2010 of the Hollywood film The Social Network. 

Facebook wasn't the first social networking site. Arguably, the first was America Online, founded under this name in 1991 and currently known as AOL. The first social networking site proper was SixDegrees.com, founded in 1997, followed by Makeoutclub in 2000 and Friendster in 2002. 

The first widely popular social networking site was Myspace (at the time spelled MySpace), which launched in 2003, six months before Facebook. It took Facebook until 2008 to overtake Myspace in popularity. Facebook introduced its now ubiquitous "Like" feature in 2009. 

Facebook celebrated its 10-year anniversary with the introduction of a feature called Look Back. Active users can post a personalized movie or collection of photos of their posting highlights since joining Facebook. 

Along the way Facebook has received its share of criticism, and it still does. It changes its interface, which is anything but simple, too often for many users, forcing you to learn new ways. It has a loosey-goosey approach to privacy, collecting lots of data on users and bombarding them with ads. Despite the criticism, Facebook's advertising revenue has grown exponentially. 

If you're not careful, as with a number of other online activities, you can get scammed or otherwise harmed through Facebook. 

One scam involves Facebook's Like, its thumbs-up button. Likes can generate ad revenue for the business or individual behind the particular Facebook page. Any attempt to sell you Likes, clicked by real people, are a scam. Facebook's policies prohibit this practice. 

According to Facebook's help system, "Certain websites promise to provide large numbers of likes for your Page if you sign up and give them money. These websites typically use deceptive practices or are scams." 

Another scam involves a "You gotta see this!" or similar message. When you click on it, you're asked through a pop-up window to download a media player. Only the download is "malware" that steals your data, your identity, or your money. 

The Facebook section of Hoax-Slayer (www.hoax-slayer.com/facebook-related.html) has more detailed information about Facebook-related scams and hoaxes. 

Facebook isn't the only social networking site in town. The most prominent competing services include Twitter (www.twitter.com), Google+https://plus.google.com/), and LinkedIn (www.linkedin.com). 

Twitter specializes in letting you send and read "tweets," which are text messages of up to 140 characters. You can update your followers with news of anything from your recent job promotion or upcoming marriage to your thoughts about the movie you just saw or what you had for dinner. 

Google+ attempts to leverage Google's other services, from search and online storage to email and cloud software. 

LinkedIn is targeted for "professional networking," to help companies and business people make new contacts and keep in touch with previous co-workers, affiliates, and clients. 

The social media world is constantly in flux. In February Twitter began testing an experimental interface with a select group of users that's a cross between Facebook and Google+. 

To avoid flaming out like Myspace and AOL did before it, Facebook in the future needs to remain cutting edge and cool with teens and other young people. It has to resist the temptation of getting ever more aggressive in monetizing every last piece of screen real estate, which eventually could chase away users in droves. 

Today, Facebook is arguably the second most prominent online presence, behind Google's search engine. In the ever-changing online world, it's an open question whether this will remain the case.