Q: During an interview with a recruiter I mentioned several people I had worked with in past jobs. I made reference to these colleagues in discussing my experience and accomplishments. As part of the search process, I provided the recruiter with three 
references he requested. But later I found out he had also called those people I mentioned in the interview. Is this ethical?
A: Calling references not on your “official” reference list is called secondary referencing. Yes, it is ethical as long as they do not call someone who will violate the confidentiality of your job search. This process is becoming more common as recruiters and employers seek to gain a more complete picture of the person they plan to hire. A hiring mistake is very costly, not only to the employer but the candidate as well, so there is growing pressure, especially in the new healthcare reform environment, not pick the wrong person.
Look at it this way. When someone agrees to be a reference, they want to be of help. You are not going to knowingly submit references who will say bad things about you. Because they want to help, candidate submitted references almost always focus on your positive attributes. Only rarely, perhaps one time in 50, will a reference say things that will derail a job offer.
So, recruiters and employers must dig deeper. Contacting secondary references is one of the ways recruiters can gain a better understanding of who you are, your leadership style and whether you actually accomplished all the things you claim to have done. The days of lying on the resume with phony degrees or credentials are over. Today the biggest risk for misrepresentation or outright lying on the resume is through the embellishment of experience and/or accomplishments. Unfortunately, that is more common than most people think.
Good recruiters are going to be very cautious when calling secondary references because they want to protect your confidentiality in the search. But a smart move in the interview is never to refer to anyone you currently work with and never mention the name of someone who may hold a grudge. It is also perfectly appropriate to ask the recruiter to give you a heads up before references are called so that you can alert them.