I use fb for my family mainly. Most all of them live in Florida so it's nice to talk to them everyday. I try to keep it very clean on there. All I need is for grandma or my little family members to see me typing fugity fug fug dick sucker poo head bastard.
My favorite huddlers are on my fb too as well as close friends. I'm not one for friending everyone on the planet so if you're my fb friend I actually do like you and trust that you wont post stupid poo for granny & little ones to see. You will most likely see what I'm really like irl on fb. Which is pretty much a boring housewife who posts stuff about my kid, pets, husband, food & pinterest all the time.
I have a google+ and linkedin but don't use them. It's too much to keep up with.
I mostly use my facebook for entertainment purposes - either because I just had some random thought and needed to share with someone or because I had a question I needed an answer to (yes, there's google but people I know who know my capabilities is usually better - like when I almost burnt down my house this weekend) or to promote my business / a friend's business.
I RARELY put anything serious out there. I am currently going through a possible major life-change but other than a vague comment here and there, I don't even want to post about it. Too much negativity. The people closest to me will know what a vague post is about, maybe.
LinkedIn has proven helpful in networking for jobs, getting some inside info on a potential employer, stuff like that.
I don't use Google thingy.