I have been a huge fan of LinkedIn for a number of years. In that time, I've noticed a phenomenon about LinkedIn invitations. Every now and again, someone new joins and invites their friends. This causes a short burst, or wave, of new LinkedIn subscribers and invitations. These waves seem to last about three days.
One of the key reasons people start to use LinkedIn is to beef up their networks to explore a job search. If you see more of these waves in your company, you might start to wonder if people are becoming unhappy enough to look around. These waves could be an early warning sign of future attrition.
I may be starting my own little wave here: If you aren't using LinkedIn already, you should be. It is a great tool even if you aren't looking for a job. Once your network is in place you can see the subscription activity in your network by looking at your home page in the tool.