AS far as Kyle Stoneman is concerned, the campus police were the ones who started the Facebook wars. "We were just being, well, college students, and they used it against us," says Mr. Stoneman, a senior at George Washington University in Washington. He is convinced that the campus security force got wind of a party he and some buddies were planning last year by monitoring Facebook.com, the phenomenally popular college networking site. The officers waited till the shindig was in full swing, Mr. Stoneman grouses, then shut it down on discovering under-age drinking.

Mr. Stoneman and his friends decided to fight back. Their weapon of choice? Facebook, of course.

Once again they used the site, which is visited by more than 80 percent of the student body, to chat up a beer blast. But this time, when the campus police showed up, they found 40 students and a table of cake and cookies, all decorated with the word "beer." "We even set up a cake-pong table," a twist on the beer-pong drinking game, he says. "The look on the faces of the cops was priceless." As the coup de grâce, he posted photographs of the party on Facebook, including a portrait of one nonplussed officer.

A university spokesman, Tracy Schario, insists that noise complaints, not nosing around Facebook, led the police to both parties. But, she says, "it's sort of an inevitability that if a party is talked about on the site, word of it will reach the enforcement people, who then have no choice but to investigate." In fact, two campus police officers and the chief's assistant are among the 14,000 Facebook members at George Washington.

The stunt could be read as a sign that Facebook has become more than a way for young people to stay in touch. Started in 2004 by Harvard students who wanted to animate the black-and-white thumbnail photos of freshman directories, the site is the ninth most visited on the Internet, according to Nielsen/Net Ratings, and is used by nearly five million college students. Facebook is available at most of the country's four-year colleges, and many two-year colleges, too.