I recently wrote a Research Brief on "Social Media" that discusses the issue and provides links to resources that principals can use to reduce the negative effects of social networking. You may want to take a look at the strategies recommended for schools.
As with most technology, there is a positive side and many schools have begun to use social media to improve communication with families and community, to improve instruction, and to access curricular resources. Many of these ideas are also included in the brief.
I would enjoy hearing from you about the challenges, as well as the benefits, you face in using social media.