I knew one person who felt bad turning down people's friend requests, so they would always add them - and people added for random reasons, like, just if they happened to meet them at a party or an event. Actually, there was one person whom he didn't even know - it was this "mystery" guy who had added himself to various people we knew, but I bet nobody even knew who it was, lol!
Now, I think most NTs don't confuse the "facebook friend" with real, actual friend - so he didn't really think much of it. And I know other people who just add "facebook friends" as contacts/network, so it's just useful for them.
Now, another person I knew had over 3000 friends - and she was always posting pictures of herself in a bikini, licking ice cream, all kinds of shots that showcased her beauty, and then she had male and female admirers alike flattering her like she was a goddess. Everything she posted, whether it was happy or sad, was entirely focused on herself, and gaining people's reactions. I think she was a narcissist, very unpleasant to deal with underneath those lovely, heavily lined eyelids! She could come off however she wanted online, but she was so awful in person, I'm sorry. Perfectly happy when all attention was on her and when she was getting everything her way - but the slightest deviation from worshipping her, and watch out! Once she was unfairly attacking me, and her husband stood up for me - well, that was that. After that she was so mean to me it was awful, she actually even accused me of harboring the devil. SO. (This was one of the crazy people that aided my decision to get off of facebook. She even pestered me about why she couldn't access my photos when I was dealing with my mother's funeral arrangements.) Those are the two sides of the spectrum when it comes to why people have 1000 "friends"! I think most just think of it as a network, not real friends - others are totally self-centered and want a private audience to show off to.