On a serious note, pretty much everyone suffers from low self-asteem now and again, and people now manifest that feeling towards FB.
I myself constantly check FB during the day, its a way of having a laugh and keeping up to date with people, and reading any funny links and/or videos that might be posted, sometimes its the only 'socialising' I can do!
Self promotion has always been around, or the need to let people know what they've recently done or got, FB just makes it a lot more easier and blatant I guess.
ADD ME I WANT MOAR FRIENDS LOL.