"What can an employer do? Only the best they can. Do perform interviews. Do test skills, intelligence, and other factors. But, realize that this is still very flawed. If a candidate comes in with an awesome recommendation from someone you trust and who has actually worked closely with that candidate, hire her — even if her interview was just okay."

Well said, and made me want to know more about the author, Gayle Laakmann McDowell, Ex-Googler, Author of Cracking the Coding Interview and The Google Resume.

Inspired by this NYT article.

If a candidate comes in with an awesome recommendation from someone you trust and who has actually worked closely with that candidate, hire her — even if her interview was just okay."  

that seems to go against the grain of other postings on hiring. plus it probably does not help diversity when an okay interview from a trusted source is better than outstanding interviews? 

Interviewing okay does not correlate with working ok. 

If she's known to work well, hire her. 

Jared has a very good point about diversity, and hiring "friends" is one of the reasons for homogeneous environments.  On the other hand, there is data that shows that referrals are really the best source for hiring.  Besides, people like working with people they like - there is also data that enjoying your coworkers is (almost) the best indicator of happiness at workplace.  So there is not wonder that achieving diversity is difficult.