I use Facebook exclusively for family, extended family, or friends of family. It keeps it all in one place to make it simple to keep up on. But on Facebook I'm especially careful to watch what I say. Family tends to be especially sensitive.
Usually I only log on once a week. Then I greatly limit how much time I spend catching up. Otherwise I might log on to share something newsworthy. Lord knows I could spend all day uploading cat pictures or sharing fish related videos.
Friends and acquaintances, I either only see in person or only talk to through certain forums. These places might be more public than facebook but I can vent with less risk of offending someone specifically. Here is one of those places.