LinkedIn is the best social network for your career, whether you want to use it to find a job or boost your potential. It's not without its annoyances, however. If you're prepping your profile for the job hunt especially, you'll want to head to this setting on LinkedIn first, before everything turns to hell.
The setting is related to the "Say congrats on the new job!" notices that pop up on LinkedIn and your email inbox all the time. If you don't change it, every time you tweak your title (say, to be more specific to the kind of job you're looking for next), LinkedIn will tell your network, and everyone will assume you've just landed a new position. That's not really great if you're in the midst of looking for a new position and interviewing with companies while you adjust your LinkedIn profile.
Donna Sapolin writes on Forbes that even her mother congratulated her for the "new job" and "promotion" because she changed the field under her name. To prevent this, you have to turn off activity broadcasts completely under Settings > Profile > Privacy Controls > Turn on/off your activity broadcasts.
That way, no one else in your network will mistake editing your profile with a new job. Turn it back on when you're done so the status updates and whatever else you do want to share get seen.