Do you use Facebook regularly in your classroom? How and Why?

I do not have a Facebook account and so I can’t use Facebook in my classroom.  In our school, teachers do not Friend students at least until they graduate and so it is not such a useful tool for us on a regular basis.  On the flip side, students spend much time on Facebook and are so familiar with how it can be used that I understand why some people are trying to use it in their classrooms.  We have a teacher who gave an assignment where students had to create a Facebook account/profile for a Talmudic figure.  This must have required her to have an account (but perhaps a different account than her personal account?) and for students to invite her to Friend their Talmudic figure.  I am curious if any of you use Facebook regularly in your classrooms as a way to communicate with your students and to send them reminders, etc. – If so, how do you protect your privacy and theirs?  Why have you choosen to use it rather than Edmodo or Wikispaces?