I like to think that I am interviewing the person and not the company. And the person defines the engineer and not the company they work for.
I try to treat everyone the same, if nothing else, but to have a baseline. Of course, I'm biased, but more towards referrals.
This makes me wonder, do some people treat those coming from a tier-100000000 company differently? Are there companies that someone might work for that would have a negative effect on them?