Advice from "The Departed"
There's a great scene in "The Departed" when Frank is trying to determine the rat in his organization; he asks himself "Who can do what I can do?" And that fellow financial farmers, is a great litmus test that should be incorporated into your own decision-making process when determining security selection. I think it is a valuable tool to ponder "What company can do what XXX can do?" And if you find yourself without an answer, that's a GOOD sign. It implies that XXX is indeed in possession of some type of monopolistic ability, base, location, or combination therein.
A good read on this subject is "Zero to One" which similarly identifies all monopolies as being all different in their excellence. Check it out!