Ask HN: Backdoor References for Employers?

VCs love backdoor references as a method of vetting founders. This has always rubbed me the wrong way, maybe because of the VC/founder power imbalance. However, I wonder if and when backdoor reference checks can be appropriate when vetting a prospective employer. Say you are considering joining the startup of a well known (but not to you personally) founder. Is it appropriate to try some backdoor reference checks in this case? Any pitfalls or protocol one should be aware of?