PC Maffey describes it like it is:
Hiring is broken. People leave their jobs every 2 years or less. The corporate work culture survives on people's fears. If you don't play by the rules of the people in power, how will you make money, how will you feed your family, how will you contribute to society? It's a vicious cycle perpetuated by our willingness to outsource our values.
I can’t remember if LinkedIn (or XING in German-speaking countries for that matter) ever helped me in finding or steering me towards a job.
Twitter on the other side helped me find my first one right after university (article on when I left said first job).