When I was in kindergarten, our teacher, Mrs. Landreth, created a class phonebook for us. It listed every kid in the class along with their phone numbers, and every kid got a copy. Well, this was very exciting. Now, we could call each other! The room erupted with the sounds of "I'll call you!" and "No, I'll call you!" Everybody was making plans to call someone else, or perhaps several someones. Nobody offered to call me, though, so, feeling left out, I desperately turned to the only other kid who hadn't been offered a phone call, which was Jimmy, a kid that nobody liked because he was stupid, and offered to call him. Somehow, the fact that we hitherto could have simply asked each other for our phone numbers never occurred to us.
Well, naturally, when I got home, calling Jimmy was the last thing on my mind. So when he inevitably called me to remind me that I had told him I'd call him, all I could say was, "Well, I didn't mean it" (give me a break, I was six).
This is what Facebook is. Facebook is my kindergarten phone book. But instead of a book, it's a web site. And instead of a kindergarten class, it's everyone you've ever met in your entire life. And instead of Jimmy, it's some random person you went to high school with.
Or, actually, it could be Jimmy. I'm sure he would have shown up on my Facebook eventually if I hadn't bailed, even though I haven't seen him in 30 years.