I think it depends on the skill set you offer. I’m a technical writer, (bids, proposals, grant writing, etc. It hasn’t paid off for me. I find I invest far more time with little or no ROI. I think times have changed, and certain career focuses (like Project Management) are the types of jobs you may be referring to. LinkedIn isn’t for all careers. It reminds me a lot of Elance and Upwork. It’s over-saturated and can’t replace local engagement.