Every teacher I know has their own facebook policy. I really think this is best.
Most teachers that I know have separate facebook accounts. One is for being friends with the students, and one is personal. I know one person that even uses facebook to discuss assignments during off-work hours. It's an easy way for her to make sure that the students see what she posts.
I can't figure out why a law would be needed here.
This is the major problem I see with it - students registered with Facebook and friends with the teacher would receive more attention and help than students that didn't accept the terms and conditions of Facebook (a private company). This law sounds good to me!
Modeling paged and segmented memories is tricky business. -- P.J. Denning