Not in the Job Description
Let's say that you saw an employer with a job opening that appealed to you. The employer wasn't sure that you were a good fit for the job so the two of you meet a few times to get a feel for things. If the employer decided you weren't right for the job, most times your professional relationship would end there. Let's, for the sake of argument, also say that the employer liked you enough to want to keep in contact for possible future openings. There would be several lines you wouldn't cross and certain proper decorum. For example, it would be really bad form for the employer to talk about how great the person he hired instead of you is. It would also be out of line to complain about how much of an asshole the guy he hired instead of you is. Pretty much anything having to do with that job is off-limits for conversation.
Dating is like a job interview process. The same rules and decorum applies. If you don't want to date me, fine. But I sure as hell don't want to here about the poor sap you are dating instead of me and I'm definitely not interested in acting as mediator to solve your love life problems.