Recently a client sent me an email saying that his referees made him lose out on a job opening. After his second interview with the hiring company, he got a call stating that all that was left were the formalities from his referees. A day later a regret call came in. The company had decided to go with somebody else.
Why? Because one of the referees he had listed, said something negative about him.
The referees you include in your CV are as important as the qualifications you list on your CV, that determine if you are the best fit for the job or not. For this reason, it is important you familiarize with the role referees play.