In the perfect world where you only use systems you understand, the provider of the system is completely forthcoming with telling you how it works, including the limitations and things it can't do. (I suppose Richard Stallman would be the king in that world)
In the real world, sales and PR departments will shriek like banshees on a moonless night if you use the word "limitation" when describing your system.
By the way, do you understand how your city water and sewer systems work? I mean, REALLY understand it?