Facebook.com, the online directory of colleges that acts as telephone book, yearbook and social hub all in one, has many students hooked.

"I don't really know anyone who doesn't have it," says Sheila Umayam, a junior at Middle Tennessee State University in Murfreesboro. "Maybe one or two people don't have it. It's really addictive. It really distracts you from your schoolwork and other things."

As obsessions go, this one's virtually harmless, if you don't count the hours students spend trolling cyberspace rather than studying. It has become another high-tech way for them to get the word out and keep tabs on one another.

How popular is it? So popular, it's a part of college vernacular.

" 'To facebook' is a verb here," says John Lee, a Vanderbilt University freshman in Nashville, Tenn.

As a Harvard University sophomore, Mark Zuckerberg created Facebook to help dormmates get to know one another. The site blossomed in popularity and has since spread to more than 2,100 colleges and universities. It recently added high schools and now has more than 22,000 listed.

Anyone with an ".edu" e-mail address can register and get a free college profile. (Without registering, you can't even view profiles.) You can customize who can see your page, as well as what you put on it. Students are avid about posting photos, interests, personal info, plans and links to friends' Facebook profiles and Facebook groups they've joined.

The groups typically sport self-explanatory names such as "Obsessed Completely w/ THE OC!!!" and "Coffee-holics" and "People Whose Last Name Is Four Letters Long and Ends With a Consonant."

"I try to make it entertaining for other people to read, since so many people go on Facebook to procrastinate," Lee says.

The site has proved to be an unexpectedly helpful way of promoting campus events, observes Sheron Fitzgerald, a Fisk University senior and resident adviser in Nashville.

"A lot of times, people say our advertising is so poor because we normally put up posters," she says. "But recently, I advertised a program I was in charge of as an R.A., and a lot of people showed up because they saw the advertisement on Facebook."

Nor are students the only ones joining Facebook. Ralph Metcalf, MTSU's multicultural affairs director, got himself a profile in October mainly for the access to students the Facebook account gives him.

"We sent out information through snail-mail and regular e-mail, but students don't check those as regularly as Facebook," Metcalf says. "So it's easy for me to send out a message on Facebook; everybody I have a contact with will get that information."

If he hasn't heard from a student in awhile, he'll send them a note through Facebook checking in, asking how the student is doing. If students have a birthday, he'll send them a birthday salutation.

"I've learned a lot about my students by reading some of the profiles they have, and sometimes it gives me better insight of how I should advise or counsel them," he says.

Facebook allows users to send private messages or sign a student's "wall," a portion of their public profile. Students spend copious amounts of time rifling through profiles and leaving notes.

It can become a hypnotically — and notoriously — time-sucking endeavor, they admit.

"I do get annoyed in the computer lab," Umayam says. "When I'm trying to do my essay, people won't get off of the computers because they're on Facebook. That becomes a problem."