I guess it depends on what you want to get out of LinkedIn, and your situation. Personally, my relationship with colleagues/boss is such that if I think about leaving they'll know about it from me first, and if I added a recruiter as a contact they wouldn't even think about it. But apart from that, my use-case for LinkedIn is primarily connecting with people I do/have work/ed with, to help us stay connected should we need to work again in the future, and so other people can see who I know and who knows me. If and when I leave my job, I won't be looking at adverts or to be contacted by recruiters, I'll be leaving for a job offered by someone I already know in the industry.

But appreciate that for other people, they might want to use it completely differently.