I don't like to mix Facebook with teaching. Some of my friends have pages for the classes that they teach (tolerable), join their class fan pages (suck-ups!), or friend students (creepy).
At TempCollege, students were very good about maintaining proper Facebook distance from professors. My students waited until I mentioned Facebook first (5 creepy points to meeeee!), and then, quite relieved, excitedly asked me what the hell my profile picture was. (For the record, I was posed next to a statue from a previous teaching assignment, and yes, my profile picture and name are the only FB items of mine that would-be student stalkers can access.)
Undergrad then tested the waters with a "so can I see your profile?" She laughed, indicated that she was joking....sort of.
I informed the crowd of upperclassmen my (very standard, I think) FB policy: I accept friend requests only after a student graduates.
They excitedly pointed out that I would be departing TempCollege in mere months. I agreed to modify my policy. I will accept friend requests after a student graduates or after I leave the institution.
The friend requests came pretty much the day after graduation. The others informed me that they had my departure date marked on their calendars (by calendar I assumed they meant electronically on their iPhones, not on an actual paper calendar... I mean, do people even use those anymore?).
"Aw," I said, "that's nice that you want to be sure that you tell me bye."
"No, Dr. Reaction! It's so we remember to facebook you!!"
Did I mention how much I miss my students?