On campuses everywhere, Facebook is bigger than binge drinking. That is a good thing, but the company's recent decision to extend beyond colleges presents graduates with a problem potentially even more destructive than underage drinking: overage Facebooking. Facebook's beauty was the community of like-minded users to which it catered. Now, the company has decided to expand its focus and invite users of all ages to join the fray. Bad idea. Facebook is killing the originality of its community.

If Facebook wants to use its technology to help people who aren't college students network, it should rebrand itself or even launch a separate site. Perhaps to TheBigChill.com? Maybe give users the option of connecting across networks, the way The Knot does for wedding planners. Once married, they are dumped into The Nest.

I am not trying to keep the 50-something, married software engineer away from the 17-year old coed cheerleader majoring in Art History—although maybe I should be. I simply believe there is far more value for the people of the Facebook community if Facebook the company continues to focus on the college students who made it successful.

Social-networking sites want as many people to sign up as possible, so they can make the most money before they sell to Google or Yahoo!. But that doesn't mean you should join. My advice is to follow a few simple rules before you sign up for any old network. Bear in mind, these aren't the companies' stated rules—they are mine. They tend to break down by age range. Check them out, after the jump.

MySpace
(teens/young adults, 14 to 30 years old)

MySpace is the gateway social-networking service—there is nothing wrong with passing through it, but make sure you get to the other side. It's garish, loud, and infinitely customizable. Almost everybody I know, of every age, has a MySpace page. Officially, you have to be 14 years old to sign up, but my stepson signed up when he was 11 and simply claimed to be 100 years old. If you are older than 30, it is time to move on. Leave the page up as a testament to your youth, but it is time to put away childish things.

There are two exceptions to this rule. First, if you are a musician, a MySpace page is job requirement. MySpace made its bones helping bands connect with fans, and it remains one of the best ways for bands to reach fans. I would also make an exception for political candidates, though I don't really believe Rudy Giuliani and Hillary Clinton are staying up late updating their Top 8s. These Potemkin pages may be a farce, but they're still better than having kids get all their political information from South Park.

Friendster
(old Friendster users, 25 to 35)

It isn't that no one under 25 should have a Friendster page; it's just that no one under 25 has one. The company claims to have more than 48 million members, but I bet most of those pages haven't been updated in a long time. Industry reports claims page views are rising, but it seems to me Facebook and MySpace are stealing Friendster's lunch—and eating it at the cool kids' table.

LinkedIn.com
(professionals, 22 to 80)

LinkedIn is designed for business networking and makes it pretty easy to connect to your peers and keep your professional history online. Just don't try to use it for romance. This is a place to do business.

eHarmony
(straight singles, 35 to 60)

After you put your single ways—or that first marriage—behind you, eHarmony is the place to go for romantic compatibility. Unfortunately, the site doesn't offer any options for gay people. Founder Neil Clark Warren says it is because he hasn't done enough research into same-sex relationships to provide accurate matches. Yahoo! and Match.com will gladly fill in the gap.

aSmallWorld
(beautiful, rich, and powerful of any age)

For the most exclusive social network, you can try to get into aSmallWorld. Whereas most networking services want to do everything to get you to sign up, aSmallWorld probably won't let you pass the home page. To join you have to be invited by a trusted member. Once past the virtual velvet rope, you are presumably treated to pop-ups for high-end cognac and oceanfront real-estate in the Hamptons. I will report back as soon as my invite arrives.

There is a community for everyone, every reason, and every season online. One giant, connected, indiscriminate network would look like, well, the Web. Sure, online social networking is all the rage, but you have to know your place. Just because you get an invite doesn't mean you should accept it. Please network responsibly.

By Dan Costa