The dominating mother is not frequently used in stories, but it has incredibly powerful irony. First off, the mother image is usually one of love and life. A good mother is selfless in her care for her children, whom she literally gave life to. There are many cultures and mythologies which have some religious significance attached to the mother figure--often times connected with the creation of the world and/or the human race. This, combined with social etiquette, often gives mothers a sense of reverence and respect ("you don't talk that way to your mother!"). Mothers are often paired with images of life, plenty, and abundance because they are birth-givers. A good mother wants what is best for her children, but allows her children the freedom to choose their own path.
But these dominating mothers twist every aspect of these classical characteristics. These characters are entirely selfish, and grant false love and care only when they benefit from it. They gave life to their children--or high standing to their underlings--but her children are forever indebted to her for granting them this 'favor.' She is above everything, and rules over everyone with an iron scepter. She has wealth and abundance, but it is not because she gave birth, rather, she took the things she has. One of her greatest abilities is her knack for manipulation; she will twist her underlings into doing what she wants, because they think they want it too.
My favorite part about this character, is another level of irony. She remains in power mainly because she commands respect and obedience, which would be due to her if she were a good mother. Because of her position, she guilts her children into treating her like a birth-giving, selfless, loving mother. Everyone beneath her knows she's manipulative and selfish, but they won't dare question her because since she 'gave' them life or high standing, she can take it away. Though this mother is so obviously twisted, people treat her with love solely on the basis of the fact that she is technically a mother.
It's a shame that films, comics, tv, etc. don't use this interesting character type more often. In stories where it might be possible, for one reason or another, the character is much more commonly the mafia godfather character. You can always tell a lot about a person by how they treat their mother (guys especially). This is because when a person is around their mother, they are more prone to reverting back to their childlike/childish ways: ergo, their more natural state. Fathers have this same power, but it's much more obvious with mothers, probably rooting back to their birth-giving nature. Even good mothers have an incredible power over their children: no person of any standing doesn't cringe a little when their mother shouts at them, using their full name.