Why do people keep doing this on Facebook?

[L.i.f.e. G.o.e.s. O.n.]

I've now deactivated it because I've had enough.
-Family members keep randomly deleting me, blocking me and re-adding me and the deleting me again hours later.

-There are some old school mates that also keep re- adding me and then deleting after. The funny thing is that they are friends with all the other people from the school, even friends with the teachers. I now only have about 3 old school mates as friends which are just guys. But the girls don't seem to like me anymore as about 20 of them have deleted me even though they are the ones who added me in the first place.
And I have about 100 new friends which I met at my new College and at University.

-Some old School mates even still post statuses about me, saying that I'm a show off or something because I posted my Artwork in a Gallery. Lol

The thing about me, is that I hardly ever post much on Facebook , except a few statuses and photos of good things that have happened, etc. I never post anything negative or that would be offensive, I don't send FarmVille requests because I don't play it. I don't post things every day or 5 minutes, not to the point where I plague people's news feeds.

I've also been told by some good people, that the people who have blocked or deleted me have been writing nasty insulting statuses about me, saying that I'm ugly and shouldn't be getting on with my life.

I just don't understand Facebook anymore, because it seems like people just want to cause trouble probably because they are insecure with themselves. So for now on I've just completely deactivated it, I don't even feel safe on it and feel that my reputation has been ruined too because of the people insulting me on it..
Whatever I have mentioned in this question has nothing to do with emails or privacy problems.

My Facebook is constantly kept on private too.