I don't accept Facebook friend requests from students... or their parents! (I had a couple of those this year too.) I already censor myself on Facebook now that my coworkers (and boss) and older family members are on there, but I would feel even more obligated to make sure everything I posted or "liked" was appropriate if I knew my students and their parents could see it, and that would take all the fun out of it. My first class of students are going to be juniors in high school this year... I figure when they get out of high school, if they still want to be Facebook friends, I'll friend them then, when we're all adults LOL.