Based on experience, here’s some advice: Be nice to the people with whom you work (and everyone else for that matter)! You never know when a prospective employer might ask them about you without you knowing. It is just SO EASY to find people you might know in common, so let’s face it, why would a prospective employer not do it?
If you are in the job market, whoever is reading your CV might know people in common with you which means they might take the liberty to contact these people to ask about you. If this happens, it may well be a determining factor as to whether or not the employer ever meets with you. I have seen this happen several times. Recently I submitted a candidate’s profile to an employer. In my interview with the candidate, he told me, (with conviction!) that his references were stellar. Imagine my surprise when the employer would not meet with the candidate because they had “…called some people they know in common and the feedback was negative”. Well that was the end of that for the candidate. There was no interview, no ‘let’s see if there is a fit and if we can work together’. Zero. Nothing. The candidate’s stellar references were ultimately irrelevant. He never even got an interview let alone the opportunity to present his (hand picked) stellar references.
Reference checking starts at any point during the hiring process. Providing references to a prospective employer is definitely still one of the steps of a traditional hiring process, but it is less and less meaningful since employers really have access to the unedited list. If they feel they know someone well enough, best to assume they will contact that person.
Candidates should know what the person who likes them the least might say about them.
One question I ask in every interview is “if I speak to someone who would not want to work with you again, why would that be”? Often the candidate has to think about it, which is perfectly fine. I can see they are digging deep to find the words to tell me they can be aggressive, competitive or disorganized, for example. I also ask them what words, in general, people would use to describe them. Note that I don’t ask about their “weakness” (what does that even mean…really…what a lousy question. My weakness is Finance. Why people would not want to work with me again has nothing to do with Finance). I want to hear how people believe they are perceived and then I match that up with what I hear from the references I contact.
If you are in the market, be prepared. You are not able to control who speaks to who. What you can control is having a clear sense of who you are, especially to the people with whom you work so the feedback a prospective employer gets will align with how you describe and present yourself.