Most of it is showing off, yeah. I do find myself checking my Facebook regularly, even tho I don't actually like it. I hate seeing people posting pics of them having a good time. It's not that I don't have a good time, but literally the only reason why people do this (and this is not just my opinion, it's true) is to make people jealous and show them how awesome your life is (at that given moment, because obviously the only thing they post are the fun parts).
On the other hand, I find some posts hilarious, especially the relationship crap. I almost never post stuff, but when I do, it's mostly ironic stuff to make fun of these people who are posting bullcrap in order to get people jealous. Most of my actual friends think it's pretty hilarious too. For example, I take a dumb stereotypical pic when I go out or i.e. when I'm eating Ben&jerry's, and caption it with "LOOK HOW SUPER AWESOME MY LIFE IS OMG!!!!!!!!!!!!!!!" or something like that. Or I post a stupid hipster pic or one of these dumb quotes (like "keep calm and be awesome") and make some kind of ironic caption. Thats my way to deal with all this nonsense. Just sabotage it, when people read it they usually know it's ironic/sarcastic as fresia and they'll probably realise I'm making fun of them. Sometimes I comment on a status that is purely to make people jealous (for example, a group of people I don't actually like that's on vacation who post all kinds pictures of them having fun). You'll risk everyone hating you and saying horrible things back, but the key is to not really care. I also hardly ever lose a discussion and have enough people to back me up anyway, and as I said, I just don't give a crap about them and they know it.
This might not work for everyone, but it does for me, and it can be very satisfying.
An other thing to do is just delete facebook. I thought about it and I might just do it, but it's also a way of communicating with people for me. I use the chat pretty often, and it's also useful for events and stuff.