Although it's been mentioned in individual talks, social networking has only been directly addressed in a few publications:
http://www.watchtower.org/e/200703/article_02.htm -- "As with any mode of communication, online social networks can have legitimate uses as well as potential abuses. ... Rather than simply condemn the Internet, parents would do well to familiarize themselves with the sites that their children frequent."
http://www.watchtower.org/e/200810/article_02.htm -- "'A social networking site is like an online party,' says a girl named Joanna. 'Some very scary people can show up.' The personal information posted on social networks can be exploited by unscrupulous youths and adults. Thus, Internet safety expert Parry Aftab calls such sites 'one stop shopping for sexual predators.' ... Thus, 'What in the World Are Your Kids Doing Online?' asks a valid question: 'How do you make it clear that children need to develop empathy and compassion when the electronic world allows them to meet and discard people at the drop of a hat?'"
http://www.watchtower.org/e/200703/article_01.htm -- "[M]any youths are wandering alone in the online neighborhood, and some are creating social networks with people whom you—and even your child—would never invite into the home."
So it's not outright condemned, but it's also strongly discouraged. It's also clear that they worry more about young ones using social networking sites than adults.
I do wonder how long they can go without establishing an official presence on major social networking websites. They can't miss that PR opportunity, but at the same time, they also can't be seen as approving or endorsing their use for members. I do know there's some type of YouTube account now, though, so maybe they're moving in that direction.
