I suggest you look at THE Journal, an educational technology based journal.
I am in a technology class at the moment and we have found many different ways to incorporate twitter and Facebook in classrooms. http://http://brianjdixon.com/facebook_in_classroom Gives some reasons and a different look on why or how facebook can be beneficial. In class we discussed incorporating facebook into our lesson plans. For example, when discussing main characters in a book students can create "facebook pages" for these characters getting a better understanding of the content they are reading. We also brought up and tried using twitter in a live feed during a discussion in class. As the teacher you can hold the main page up on a whiteboard or projector and have the students comment as a discussion. This I found was beneficial at keeping track of those paying attention and letting everyones option be heard. Having these technologies allows them to use a some what simple lesson and apply a modern day twist on learning. Lets face it social networking is not going out of business anytime soon, and can be utilized in a manner that is extremely educational.
Please let me know if this helps
I am a social media strategist and therefore am very keen for people to embrace this medium. Facebook for Educators is a great resource and Facebook are keen to outline their privacy statements: https://www.facebook.com/FBforEducators
If you look at our twitter accout www.twitter.com/eteach there are lists whereby Schools and Teachers can share resources and also share revision via blogs. I have seen colleges and schools grow on Twitter where they can tweet messages to parents and students. Plus some great development for staff to share ideas and gain insight from other schools.
This might also help; an article on mashable http://mashable.com/2010/09/29/social-media-in-school/