Hypocritical employers
I once worked a contract gig for a major defense contractor. When my gig ended, I asked a FTE colleagues if I could use him as a reference. He said that it was against company policy for *any* employee to give a reference. He also mentioned that when he himself was hired, he was asked for references!
I now only give out the name of one former fellow contractor, and none of the FTE colleagues - even those that worked at companies that do not have such a policy - and simply use the excuse that I do not want to cause any potential problems with former colleagues. I have had other fellow contractors, but they were all H1B/L1 Indians ...
Of course, I have been unemployed since that gig in question, but I have not even had a nibble, so I can't say if this has hurt me or not.