The only real use I make of LinkedIn is as a source of questions. I enjoy trying to work up worthwhile answers. My principal criticism of LinkedIn, conditioned on my own use of it, is that it holds the copyrights to questions and answers.
I saw this video at Grincheux, aux barricades!. See Harold Jarche at The Curmudgeon’s Manifesto for further comment about how we should own and share what we do on the ‘net.