Abusing a Facebook function where you can "like" a friend's status or wall activity.
Like raping would consist of liking at least the last 50 activity notes on any one person's profile page, resulting in a copious and rather annoying amount of activity notifications.
Michelle: I just logged on to Facebook and I had 843 notifications. What the hell is going on?
Lee: Haha, Sam must've like raped you.
Michelle: Yes he did. How annoying! Now all my important notifications are lost within this rubbish.
Faye: It's Michelle's birthday today. Are you going to bake her a cake?
Sam: No, I'm going to Facebook like rape her instead.