First off: I WISH. I think that using it as a networking tool COULD be worth exploring. I understand from a liability (and time-wasting) perspective that the risks are probably too great to open up school use. So we'll experiment with use on the other side of the firewall.
Last night I dipped my toe into the Facebook pool for use with my classes. I set up a fan page for Mr. C Baker's Math Class and plan to use it as a communication tool for both students and parents and a holding place for notes, links, and resources.
My fears are not founded upon students finding incriminating photos of past transgressions (nor present). I am not concerned with crossing any lines of professionalism in interacting with students online (because I do not believe I am). I do not fear opening my classroom or teaching to criticism from the outside (because it brings accountability and transparency with it). I have been a believer even since student teaching that if you are afraid or wary of observations and eyes in your classroom, then you probably know that there are deficiencies in some manner of your teaching (and need to be humble enough to address them).
So, then, the fear I do keep is in boundaries for myself. As it is so natural for me to interact on Facebook for my personal social networking, I worry about being sucked in with the allure of building "fans," addressing students' and parents' questions, and monitoring my discussion board to see if students are using it. What can I say; I'm a sucker for unique hits. I think this is a healthy fear, however. A fear that springs from self-awareness of my weaknesses and obsessions is a fear that keeps me in check. It's a fear for improvement.
In the end, I'd say my Facebook fan page is really just an extention of having my own class website on freewebs with discussion board, or my class twitter account. I know there are many educators (including the official NEA stance on the subject) that would criticize my decision; even some close to me. I guess all I'd have to say to them, is that I reserve all rights to act now and ask for forgiveness later. I think that has to be the nature of any educator acting as an early adopter of technologies.
We'll see how it goes!