Not everything on linkedin is up-to-date or correct. Then there's the issue of some people personally knowing others but the information not being on linkedin.

Not everything on linkedin is up-to-date or correct. Then there's the issue of some people personally knowing others but the information not being on linkedin. It's pretty easy to accidentally cold call someone for references who will talk to the candidates current employer, and this may even be the reason the candidate left them off of the reference list in the first place.