> Always have the ping come from a non-recruiter.

I had the complete opposite thing happen. There is a dude I went to school with, I know him personally. We are connections on linkedin. He started a company a few years back. I get an email from a recruiter telling me the founders at Company X (his company) felt that I would be a good fit for their team. I am convinced that she just searched for some skill sets and made this form letter up just to make it sound fancy.