When one goes from being a "job seeker" on linkedin to being employed and wanting to show off to all your friends/colleagues through inviting them into your network.
Having minimal information on your profile and "in search of new career opportunity" to having a gratuitous amount of pages of text on a job you haven't even started yet.
Joe just had a linkedin explosion? Suddenly he thinks he's hot shit after landing that gig at BMW, he's adding everyone left and right bro.
Did you hear? Jill recently went from struggling liberal arts graduate to retail at Saks. She had a linkedin explosion and added our entire graduating class to brag about it through status updates.