Here is a video I created to make a case for 4 reasons Facebook is valuable in the classroom: http://www.youtube.com/
In short, it:
(a) creates a bond between teacher and student that is beneficial to the classroom environment
(b) encourages students to actively produce content rather than simply absorb like sponges
(c) its community-based format fosters discussion, reflection, social awareness, and what Stanley Fish termed the "interpretive community" effect
(d) makes students sensitive to different dialects/formalities of English
