The act of monitoring another person's activity (status updates, photo uploads, photo tags, photo comments, wall posts, friend additions, group memberships, attended events, mutual friends, e.t.c.) on the popular social network of Facebook.
Person A: I was facebook stalking Jennifer for two hours last night.
Person B: Oh really?
Person A: Yeah, Amber added photos from her birthday party and Jennifer was tagged in one of them. However two weeks ago Jennifer RSVPed 'attending' on the guest list for Jack's birthday party which was the same night as Amber's. Then she updated her status to: "Jennifer is going on a date tonight" but according to her relationship status, she's not single!