How secure a person feels in their job is inversely proportional to how active they are on LinkedIn!
Just an amusing observation. I see someone I haven't seen at all post on LinkedIn and they'll be active for a few days, announce a job change and immediately go back to hibernation!
I, myself, am guilty of it! While I try to be active on LinkedIn regardless, I do see a spike in my activity when actively soliciting a new client as opposed to when I'm comfortable with one :D