I never like FB to begin with, or Social Networks like it in general, but the thing that made me pull the trigger was the one day my greatest fear was realized:

I never like FB to begin with, or Social Networks like it in general, but the thing that made me pull the trigger was the one day my greatest fear was realized: "I don't want to find out that I hate the people that I like", and lo and behold, one day I scrolled a little too far and discovered "well, I can never think about that person in the same way again"