I've had Facebook for about 7 years now. I've never had more than 50 friends and now only use it to keep up with some of my family.
I signed up for twitter two years ago but didn't start using it til this year to try to connect with a few people in my, now chosen, profession. When you work in a field with mostly freelancers, you can say all the shyt you want as long as it's not too stupid.
Never had instagram but that's just mostly cause I'm only now getting comfortable with posting my life on the internet. Not ready for that step, though.
Not too worried about the whole leaking thing because I actually think before I post anything pertaining to my life. And anything I don't want people to know, I just don't post.
It also helps if you have little interest and little time in what other people post. I spend about 2 or 3 minutes going through my twitter timeline looking for things to favorite and possibly retweet. And that's only when I post, which is about every few days. It's not much of a fuss, really.