If parents and teachers are connected on social networking websites, they can be in touch all the time about their child's behaviour and progress. This can eliminate the need for yearly parent teacher conferences, instead spreading those interactions out over time. It can also serve as a way for parents to deliver sick notes to teachers, as long as they keep their accounts secure from the students in question.
The caveat here is that I am neither a teacher nor a parent (or even a social networker of any regard), so I don't know how well it would work on either side. It just seems to me that reducing the communication burden between parents and teachers would probably be a good thing. A similar arrangement would be suitable for the parents of children's friends.
Mokalus of Borg
PS - This is where the neighbourhood went.
PPS - Online.