What about the bias that comes from having worked with someone for a few years, and knowing without any doubt that they are awesomely gifted, loyal to a fault, and willing to dive into the breach for the common cause? You cannot figure that out with a sterile interviewing process.

A company does not have to guard against 'bias' other than racial, religious and that sort of thing. 'Bias' towards (or against) people you know is called knowledge.