It rattled a few readers when I said that most law professors at any law school from the 20th on down are fungible. What I meant that any could leave and their absence would hardly be noted. It is actually pretty extreme. At my school one very productive and self-promoting type left as did another far less productive but equally self- promoting. In the case of one there was hand-wringing including some of my own. In the case of another there was more than a modicum of relief. Years have now passed and I could count on one finger the number of times their absence has been noted by fellow faculty. I could count on no fingers the number of times a student or alum has expressed regret at the loss.
This just raises the question of why deans will sometimes fight so hard to keep people by giving into their demands. For example, "give my spouse a job or I will leave" or "I must teach X or I will leave." Even assuming these are not idle threats I can think of only two reason to cave in -- the person teaches a course for which it is hard to find teachers (this makes them a bit less fungible) or the transaction costs of finding the replacement exceeds the cost of granting whatever is demanded. Let's face it, someone with an actual better offer is going to leave anyway. Those who make demands based on the threat of leaving have, at best, a marginally better offer.
Coming to grips with one's ease of replacement is not easy. On the other hand, it does make you take yourself a little less seriously. For a law prof that is not a small improvement.