Earlier quoted context omitted.
Lots of people use it. The feed aspect of it is useless. But in terms of a network it's great. I've found 2 out of my last 3 jobs there. Assume it's also great for organic marketing as well where you target associates of your current clients.
So it's a digital rolodex. That's not terribly impressive for the weight of the name.
It's an automatically-updating and linked rolodex. Rolodexes tell you that you know X. They don't say who X knows.